Disappointing maiden run with 10" Dob

[darkskybondi]

The skies were clear for twilight and a couple of stars and a planet or two were out, so I took the new SW truss dob out on the patio for a test run. I suspect the main problem is my incompetence at collimation, although I should mention that I took the store's display model as they said they didn't have any boxed ones out back. As such I don't know if anything is wrong with it except that the mirrors have a bit of dust etc on them - though not a great deal.

When I collimated using the GSO laser collimator from York, I first centred the laser beam in the centre of the primary. Then I tried to get the laser dot in the sausage on the collimator by turning the 3 adjustment screws on the primary. I should mention that the 3 locking screws were reasonably firm throughout. I was annoyed because two of the adjusting screws were tight as a tiger, and when I moved the third screw so that the dot would centre, the third screw was so loose that it just stopped being effective. So I recollimated the secondary and tried again with the primary. Bingo - I got the dot in the sausage and took the scope out shortly after.

Now the finder scope didn't blow my socks off, it wouldn't completely focus for me but it was sufficient to find an object. I centred on Sirius, looked through the 10mm eyepiece... I get better views out of my 8x40 binoculars. I let the celestial sphere spin by for a minute or so and watched through the eyepiece: dim, dim, dim. I figured it must have been out of collimation so I checked it, and the primary was out, a little bit. By this time the Sydney summer evening clouds were blocking the stars and I thought it was time to come in here and complain on IIS.

A few questions:
1. Can a slightly uncollimated scope cause an awful dim view?
2. Are the people who say laser collimation is useless right?
3. Am I going to burn my darn retinas off if I stare at the alignment dot on my laser collimator (the one on the side)? It so bright!
4. Am I collimating correctly, by the sound of it?
5. Is it possible that I got sold a dud scope? What else could be wrong with it?
6:

Cheers, disappointment, here's hoping -
- DSB

[JethroB76 (Jeff)]

5. You were probably fighting a combination of some, or all of, seeing conditions, light pollution, a still-cooling mirror, poor dark adaption, possible collimation issues and your inexperience in observing

[danielsun]

As Jethro says it could be a combination of things but I'm sure that if the seeing is good and you let your eyes dark adapt you should be getting some very fine viewing through the 10".
You should be able to turn the front end (large end) of your finder scope to reach focus. I have 3 skywatcher/Saxon scopes and I remember my first view through my 8" absolutely blew me away.
I don't think with the collimation being just a little bit out would have such a big impact.
Recheck your collimation during the day and make sure every thing is tight and have another go on a clear night.
It may also have been that there may have been some light thin whispy cloud up high which will degrade viewing.

Cheers Daniel.

[GeoffW1 (Geoff)]

Originally Posted by darkskybondi

A few questions:
1. Can a slightly uncollimated scope cause an awful dim view?
2. Are the people who say laser collimation is useless right?
3. Am I going to burn my darn retinas off if I stare at the alignment dot on my laser collimator (the one on the side)? It so bright!
4. Am I collimating correctly, by the sound of it?
5. Is it possible that I got sold a dud scope? What else could be wrong with it?
6:

Cheers, disappointment, here's hoping -
- DSB

Hi,

You have landed on the right asteroid here at IIS, I got all the assistance I needed when in the same position just starting up. I have a 200mm & 300mm dob, and a 100mm refractor and am only JUST past where you are now. It will work OK.

Now a 250mm dob is a good instrument and when used correctly (you will certainly get this right without too much trouble) from Bondi you will get great views to the East. Velvet darkness!! It will need to be collimated each setup however.

To your questions:

1: No, it will just cause an apparent difficulty focussing and a lack of resolution, say between double stars like Rigel in Orion. You will get past that.

2: No, there certainly is a bit of a dialogue here about it, but barlowed laser collimation is very effective.

3: No, but do not stare directly into the laser itself.

4: No, but nearly so. Keep going. It is not as difficult as it appears just now.

5: No, almost certainly not. See, dobs by their nature are all-adjustable, and so need a bit of fiddling before use. On the other hand you get more aperture for the money, and so more light-gathering power.

Now as to what might be wrong:

- many dobs need stronger springs on the collimation adjustment screws, that was my first move and it saved me much later grief. You can get good springs in Bunnings by matching the originals plus a bit more length, or here

https://www.bintelshop.com.au/Product.aspx?ID=6492

These new springs make the mirror move more predictably and solidly when you adjust the collimation screws.

Your trouble is most likely to be that when you screw up these adjustment screws, the mirror is not moving in concert due to the weak springs. That was my problem also at first. I found that I could tighten and loosen these screws madly all night, and the mirror would not respond.

Then when you replace them, my advice is to get a 2X Barlow lens and do what is described here (now there is much debate about what method is best, but I am a fan of this method, Barlowed Laser Collimation)

http://www.astrosystems.biz/laser.htm

For your GSO laser you will need to attach a little paper disc to the front of the Barlow lens with a small hole in the dead centre to allow the laser through. It looks like this

http://www.cameraconcepts.com/barlow...ollimation.pdf

Then you do this:

1: Use the laser collimator without the Barlow lens to centre the laser dot on the centre spot of the main mirror, by adjusting the 3 screws on the secondary housing. Actually you will find you can do this easily by rotating the secondary mirror housing a little either way, and adjusting only the right-hand-most screw a small amount. Take care not to stick your greasy thumb on the secondary mirror.

2: Then mount the laser in the Barlow-lens-with-paper-disc-on-the-end, and do not be alarmed by the large fuzzy red blob which appears on the main mirror, even if it is not perfectly central. It just has to cover the centre spot so it produces a reflected image.

3: I like to use a small hand mirror then to see the relected image of the centre spot on the paper disc you put on the end of the Barlow. A dental mirror is good also. This what you want to see (the "after")

http://www.obsessiontelescopes.com/l....html#barlowed

You just adjust your collimation screws to move the reflected image of the main mirror centre spot until it is concentric on the hole in the paper on the end of the Barlow lens. This is not at all sensitive to how much wobble there might be in the laser-to-focusser mounting.

4: Tighten the locking screws on the main mirror cell gently, and you are done.

Hope this assists

Cheers

[Dog Star (Phil)]

G'day DSB and congrats on the new scope.
I think the previous replies to your questions have pretty well covered the subject but I'm wondering about the obvious - you mention that you're viewing from the balcony of your unit. Are you turning off all the lights in the room behind you? It's not just dark skies that you need for good viewing. A dark environment is essential also. Any stray light around your person will also contribute to degraded viewing.
As I say, I'm probably mentioning the obvious and if so I apologise. Mind you, my first few viewing sessions were hampered by poor viewing and it took me a while to realise that in my eagerness to start viewing, I wasn't allowing time for the mirror to cool down enough.
We're all newbies at some time.
I'm sure you'll get things sorted eventually. Good luck!

[darkskybondi]

Thanks guys - all VERY useful information. Initially I read your posts and thought, ah, it's done for, I'll have to call in the cavalry and ask a kind astronomer to take a look at my scope.

Then I thought - the skies are semi-clear, although the seeing isn't great, but I'll give it another bash because I can see Orion.

So to compensate for my inexperience, I went for the longer focal length and thought, let's see if I can spot Orion, even with an uncollimated mirror. SUCCESS! I spotted it, dropped down to the 10mm, and had a nice view. Yes, it's an easy object, and yes, I need to collimate properly (God KNOWS what I've done to the primary with my inept, tight screwing - hope I haven't buggered it totally!) but there it was: I could see 4 stars in the trapezium at 10mm focal length.

So THANK YOU all for your help. I knew I needed to go down, eat dinner, breathe, and then give it another quick bash.

TASKS FOR THE NEAR FUTURE:
- hopefully get a 2x barlow so I can collimate as you suggested Geoff.
- I'll leave the spring replacement for another time.. just want to get it rough and ready for the moment
- soon, get a high quality, short focal length eyepiece, and a wide FOV eyepiece.

THANKS AGAIN! Hope I will move from Orion to something more challenging nice and soon. IIS support is wonderful.

Cheers!
DSB

[darkskybondi]

Originally Posted by Dog Star

G'day DSB and congrats on the new scope.
I think the previous replies to your questions have pretty well covered the subject but I'm wondering about the obvious - you mention that you're viewing from the balcony of your unit. Are you turning off all the lights in the room behind you? It's not just dark skies that you need for good viewing. A dark environment is essential also. Any stray light around your person will also contribute to degraded viewing.
As I say, I'm probably mentioning the obvious and if so I apologise. Mind you, my first few viewing sessions were hampered by poor viewing and it took me a while to realise that in my eagerness to start viewing, I wasn't allowing time for the mirror to cool down enough.
We're all newbies at some time.
I'm sure you'll get things sorted eventually. Good luck!

Yes - dogstar you are absolutely right. I have all the house lights off and I am blessed with VERY dark urban skies here in my neighbourhood - the only thing apart from horizon light pollution (which kills much of my view to the south and west, but we'll get to that another day!) are a coupe of street lights from about 700 metres away. Not a big deal.

The problems as I see it were:
- I wasn't dark adjusted at all
- The seeing is not great tonight
- I am inexperienced
- Mirrors hadn't had sufficient time to cool
- The mirrors are ineptly collimated - in other words, really quite uncollimated
- the mirrors are a little dusty because mine was the display model in the shop.

However. Seeing the Orion Nebula - even though it didn't blow my socks off - gave me great faith that things will go only up from here!

CHEERS!!!

DSB

[Spanrz (Brett)]

I had somewhat of an experience tonight. Good and bad.
Waited paitently for the clouds to break it did, great, got the scope ready...Hit the sky, dam clouds...
Clear sky....Look around. Was astounded....clouds rolled in again, dam.

Clear sky for about 20 minutes, got to see m42. Blew me away. In the crap conditons, I've never seen it like that, I could make out the shadows and all. But the horsehead was a different story. Didn't spot it, but I tried so hard.

I'm back inside, victorious, but non plussed at the weather. Hey I could have been out all night....(I'm on holidays..wth).
Wife even caught a glimpse of m42, she was amazed.

But a slight downer, was the part of the dob brake (handle), one side was missing the wedge shaped plastic brake part.
And made the scope a bit loose on the altitude settings.

I bought a 2 x barlow, it made a huge difference to what I was seeing tonight.

Dark sky, did you see that youtube vid?

[Ian Robinson]

Originally Posted by darkskybondi

Yes - dogstar you are absolutely right. I have all the house lights off and I am blessed with VERY dark urban skies here in my neighbourhood - the only thing apart from horizon light pollution (which kills much of my view to the south and west, but we'll get to that another day!) are a coupe of street lights from about 700 metres away. Not a big deal.

The problems as I see it were:
- I wasn't dark adjusted at all
- The seeing is not great tonight
- I am inexperienced
- Mirrors hadn't had sufficient time to cool
- The mirrors are ineptly collimated - in other words, really quite uncollimated
- the mirrors are a little dusty because mine was the display model in the shop.

However. Seeing the Orion Nebula - even though it didn't blow my socks off - gave me great faith that things will go only up from here!

CHEERS!!!

DSB

Add maybe that your expectations were not realistic.

Probably worth taking the mirrors out and washing them (there is a right and wrong way of doing this).
Also recollimating the optics will be worthwhile. (I'd try that first before washing the mirrors , that might be all that's needed, a bit of dust on mirror is tolerable).
Dark adaption is important (at least 15-20 minutes of no bright lights) will make a huge difference.
Pretty hazy tonight here (Gateshead), can see no clouds and can see stars , but there is a lot background reflected light off the haze. I wouldn't bother getting the scope out under that kind of condition - seeing is bad.

Concentrate on objects that are relatively high above the horizon, their light passes through less atmosphere and they look better than when lower in the sky.

[Tandum (Robin)]

You can see how good your alignment is on a star by simply moving it through the focus point. It should be round on each side of focus.

[darkskybondi]

Wonderful advice from all of you, as always. Yes, I think my expectations are all over the place - I knew what to expect out of Orion neb b/c I saw it last weekend through an 8". However, I think proper collimation, cleaning the mirrors when I learn how, and a couple of high quality eyepieces will significantly enhance the experience.

While I should post the following in observations, I managed to see not only Orion, but also what appeared to be a globular cluster in the southeast (phenomenal) and I spotted Saturn at 10mm focal length. Really enjoyable, all of it.

Spanrz and others: yes I did see the youtube vid - you mean the one on laser collimation? Was helpful. I am hearing that I need a 2x barlow to properly laser collimate and will get that asap - which will nicely double my meagre eyepiece collection too. A 5mm EP and a wide FOV EP will be the next purchases on the cards. Filters (including moon filter) can wait a little bit.

Warm regards eveyrone!

- DSb

p.s. Spanrz - there is a full article in the current AS&T about catching the horsehead - worth checking out. Apparently a very hard target, and not very detailed at even 10 or 12" apertures. Let me know what you think if you read the article.

Thanks again for all the support. I am learning tonnes already and I am sure I'll be sailing along in the next couple of weeks.

[astronut (John)]

If you're not sure on collimating your scope, try www.andysshotglass.com a very good site for understanding and carrying out collimation.

[GrampianStars (Rob)]

G'day darkskybondi
It's a dob what did you expect
there's a 20" inch out on the back mountain here collecting dust and webs
to much of a hassle getting a tall 4mt ladder in the dark and shifting it
I prefer to keep my feet grounded with the 12" SCT

As for DIM 8" should be plenty BRIGHT
maybe dewing up ? that used to creep up on me

[Davekyn (David)]

Hi darkskybondi,
Just wanted to let you know that when I started with my GSO ASDX 12” Dob, I was so hung up on collimation and ran into all sorts of trouble when I first started using the scope. I soon found it was best to collimate after I had setup as even gently moving the scope from inside to outside would knock it out of alignment.

I pretty much do it exactly the way you described it in your first post above...unless I have read it wrong. I get good results now just using the GSO laser technique. I first check after setting it all up, exactly where I want it by looking down the tube and if necessary use the secondary to align up the dot in the middle of primary. I NOTE that when I get my laser dead centre in the Primary, that the GSO laser dot splits into what looks like two dots as it is centred over the O-ring sticker...(this does not seem to effect the return beam as I then check via adjusting the primary mirror screws.

I to ran into problems with tight and loose screws on the primary end of things...things were pretty tight to begin with, however as I would screw up the collimation from lack of experience, I believe it was my fault that led to a screw so loose it fell out. Basically I readjusted all the screws so they were tight and no doubt out of alignment J ... anyways I just kept at it and finally am able to rip the whole assembly apart for cleaning, put it all back together and re-align the optics with my GSO laser and nothing else. (so far I have not needed to adjust the springs however before blaming the springs and as a last resort I would also adjust the springs to redistribute the load on each collimation screw to assist in finding the sweet spot)

I am not suggesting that you should so a complete break down of your scope to learn. I just wanted to let you know, that I ran into similar problems...pretty much identical to yours and with persistence and a bit of reading on here, was able to become proficient at collimating my scope. The biggest tip I got from here was the in/out of focus technique for checking your collimation performance...I find I can tell a lot using it for my fine tuning.

When you get good at it...you will not only find stars much better to look at...but you will become better at seeing more detail in the texture of interstellar dust & the like...well that is what I tell myselfJ...I always do much better as I try to bullseye my return beam...I know some people will tell you, & perhaps they are right to some degree, that alignment only a little out will give a pretty good result...and I agree with things like the moon or other bright object, with the right mix of eye-pieces and so forth...but nothing beats perfect collimation...and I believe you can do it, with just the GSO laser and the in/out focus method...just look after the laser and it will look after you.

Excuse the rantJ...I needed to butter myself up on collimation...It took me quite a while to perfect it...but once it happens...you’ll always enjoy the challenge of perfection. You’ll find what works for...just be persistent with it is all.

Later man...
Dave

[Dave47tuc (David)]

First slow down a bit. Can't keep up with all your threads

Take your time and learn about your scope in daylight. How it moves etc.
You must loosen the locking screws on the primary b4 you adjust the mirror.
Have a look here. http://www.andysshotglass.com/Collimating.html

Watch it over a few times with your scope close by and learn what there talking about. Please take your time and learn how to use your scope and the night sky will not disappoint
Also no need to take your scope apart or wash the mirrors it's brand new

One only learns by doing.

[ngcles]

Hi Darkskybondi,

One other piece of advice that will in many ways sum-up what others have already said:

Learning to use a telescope is like learning to play a musical instrument or drive a car.

Remember that well. Pause for a moment and think of a favourite muso -- like for example Mike Oldfield. Did Mike just pick up a guitar and star playing like a pro without a moment's practice or learning?

A lot of people buy a 'scope and expect to be able to assemble and collimate it with no more difficulty than boiling the kettle.

They also expect to be able to see dozens and dozens of objects almost instantly just by waving the 'scope around at the sky -- and that everything they look at will look just like a Hubble Space Telescope image.

It isn't quite that easy but nor is it really, really hard -- so don't be discouraged. There are thousands of experienced amateur astronomers around Australia (many on this forum) who once stood in the shoes you occupy now -- and they succeeded.

Be prepared to be patient.

Be prepared to be frustrated by the weather (like you never thought was possible).

Prepare to have some bad nights when the wheels will seem to fall off everything you attempt.

Prepare to learn about how things actually look through a 'scope -- and appreciate them for what can be seen while having a little knowledge of what you are looking at. This is important: the eye and the mind's-eye should work together in tandem.

Get ready to be blown away by your first look (and your 10,000th look) at Saturn.

Its all good fun and enjoy it for the exhilarating (and at time exasperating) hobby/obsession it is!

Welcome to telescope ownership!


Best,

Les D

[PCH (Paul)]

Hi DSB,

well, all has pretty much been said. EXCEPT ...

You indicate a 5mm ep is on the shopping list. Well you already have a 10mm and you're gonna get a 2x barlow - correct?

So, you'll have a 5mm ep with those two won't you? There you go - I've saved you $75 already.

Many people avoid buying the short fl eps (like the 5mm) simply because they have a crappy little hole to look through (you'll notice the hole gets smaller as the fl of the ep gets shorter). And the eye relief is hopeless in the short fl eps as well. Instead they buy a barlow and stick with the longer fl eps which gives you the mag you want and with comfortable eye relief and a decent sized hole to look through.

Just my 2c (or was that $75)

[bmitchell82 (Brendan)]

I agree with dave... slow down.

Don't bother washing your mirror yet untill you are fully confident in collmination. unless the mirror is fully coated with dust and i mean pretty bad your views will not be hindered as much as your light pollution and location.

As for your ep's. there are only a few bands of "usefull magnification" one being around 80 - 100 next being around 150 - 180 and then somewhere around 220 - 250. Correct me if im wrong anybody, but thats where you will be viewing mainly and ide actually say you would be more in the 80 - 100 range unless you have really good dark skys and by this i mean you can see 47 tuc the LMC and SMC, Carinae by eye.

I think one thing that people do more than often is think that they can swim before they can, go to the deep end and sink. Astronomy is a life time effort, the more you do it the more you will enjoy it and you will think to youself why did i not start it earlier. Sit down relax do a bit of reading up on things to do with your scope, ask the questions what not and then youll be just fine.

Using the laser collmination technique is just fine for doing a bit of casual observing, but as you go on you will understand and identify your specific needs. I use a combination of laser/cheshire, and soon i will delve alot deeper into collmination as i will be using my newtonian for photography. CCD's are not forgiving on mis collminated optics as our brain is!

[darkskybondi]

Thanks to everyone for their advice. IIS is an incredible support network.

Just a quick response; I will be rereading all your advice again later.

Geoff, I will absolutely look into replacing the springs and screws; I will wait a couple of weeks before doing so and just see how things go. Your collimation advice, and Dave's and Dave's and others', is great. I will study it intensively and I'll be getting a sight tube and Barlow from Bintel on Friday or Saturday - the latter is both to help me with collimation and to double my eyepiece collection (thanks PCH). (Then I'll slowly buy some high quality eyepieces.) Excellent advice on eyepieces Brendan. You've helped me greatly.

Les - thanks again for your advice. I certainly didn't expect Hubble views, but perhaps my expectations last night were a bit high. As I posted, I managed to see an impressive view of Orion's nebula and Saturn in the 10mms. However, I expected there to be more detail or brightness than I saw last week in an 8" reflector pointed at Orion. I was STOKED to see Saturn, but I did expect to see more detail in the disc in the 10mm. But I won't be fazed; I'll keep practising and I really can't wait to go to a star party and really learn from experienced people like you!

I think my biggest concern last night that there might have been something wrong with the scope because it had been the display model in the store. Geoff has allayed that concern. Now I just need to be patient and practise, which is fine by me. And learn to collimate the damn thing properly!

Thanks again to all of you for your detailed responses. I really appreciate it.

Happy new year!
- DSB

[darkskybondi]

Happy new year all!

Before the 9pm fireworks I had a peek at Venus. Very, very small. I haven't looked it up but I suspect Venus is at its most distant from us right now... I'll have to check that. Anyway, I snuck off between the 9pm and midnight fireworks to look at Orion's neb. Call me crazy. Later, after 2am, I observed a bunch of stuff, including Saturn again. Madness.

At various points, I tried collimating. The laser died on me a few times. But I kept trying and I found the same thing as usual: to get the dot into the collimator's sausage, I am screwing 2 of the 3 adjusting screws really very tight, and the third adjusting screw is barely wound at all. The 2 tight ones are so tight that I even slipped with the screwdriver and tapped the back of the primary. Not good. Is this normal?

The other idiosyncrasies of my scope are the finder and the mount. The finder is hopeless. The focusing ring doesn't do anything. So it's just sort of focused, and barely helps me find objects. I find that if I screw the finder's holding screws much more than a couple of turns, the finder is completely off centre. And regarding the mount - I find that to keep the scope from moving, I am turning the handles very tight too. Very tight.

What is it about tight screws and my telescope? I don't know if any of this is normal because I really am so new to this.

Anyway, there is some frustration but I know I can always get my rocks off with some of the brighter objects, so there's easy joy whenever I need it (apparently even with a poorly collimated instrument!)

May I be one of the first to say: happy International Year of Astronomy!

- DSB

(p.s. Saturn didn't appear large or detailed in my 10mm eyepiece, but I could see 4 or 5 moons and the planet appeared crisp and clear. I don't know if this says anything to you about how well-aligned my scope is, but I thought I'd mention it.)