Expectations

[BC]

Well my new 10" dob is out of the box 4 weeks early and there have been very few clear nights. I must admit to wondering how one ever feels confident about collimation results, I've read endless articles from the web. I haven't a clue whether it's right or not. I'm also just a bit dissapointed with the views. I have pretty dark skies and was looking forward to find a galaxy or 2. I finally found the sombrero (M104) but it was just an angular smudge with a lighter smudge in the middle. I guess all the talk about seeing structure in galaxies with a 10" led me to certain expectations. It all looks so sharp through my 20 x 80 binos or through the finder, but at 40x in the telescope it's all a bit dull. hmmmmm :confused:

[astroron]

It all depends what eyepiece you are using, the Sombrero in a 30mm eyepiece even in a 16" scope is not that brilliant but using high manification comes up great, dont get dispondant just yet look at other larger objects to guage the performance of your telescope with different eyepieces and you will learn to appreciate what your scope can do. astroron :thumbsup:

[RAJAH235]

BC, What does a 'star' image look like at say, 150 x/ 200 x? Do you get good, even diffraction circles either side of focus? If not, then adjust collimation whilst on the star. Try about a mag 3 or 4.
Seeing has a lot to do with how the image looks, & how much mag you can use.
For a simple collimation guide > (http://skyandtelescope.com/printable/howto/scopes/article_790.asp)
Try 2070 (Tarantula nebula in LMC), as a starter. Should be able to resolve some of the central area.
If you're having trouble collimating, I may be able to assist with the basics,but read/print the article first.
HTH. :D L.

[ballaratdragons]

BC,

It could all come down to eyepieces. As I have found, Cheapish EP's give a fairly poor result giving the impression that the scope is no good. Even a moderate scope with very good EP's will give fairly good results.
I know what you mean about Sombrero. I can see it very easy but I see it much the way you explain it. That, I believe, is due to my lower quality EP's. Whereas the Moon give the most incredible views. I can find about 60-80 galaxies from my dark site but my EP's will not show a crisp image and it does get frustrating. My EP's are mainly Series 500's. Not very good. Whereas I can see the Orion and Tarantula nebs extremely clear. The Globulars as well. And yet Joop and Saturn look mediocre.

Dark skies are not everything either. I live in a very dark site and yet lately the seeing (on clear nights) has been terrible.
There is a lot of moisture in the air. Even though I can see the Planets and stars crystal clear with the unaided eye and also in the finder, when magnified through the scope the views are shocking. It is like trying to focus through fog!

Don't despair. Some nights are better than others and you will know when you strike a good night. You will see galaxies everywhere in Virgo for example. The Fornax Cluster of galaxies is excellent too but it is out of range at the moment.

To test the quality of your EP's find Sombrero with a low mag EP. Then place in a higher mag EP. It should appear a bit fainter but clearer. Like I said, it doesn't clear up for me but I know that my EP's aren't all that great. My scope is excellent, I just need to take advantage of better EP's one day.

Two Globs (47Tuc and Omega Cent) are very very clear for me at all mags. Try them too.

[cahullian]

BC don't expect to see images like those taken by the Hubble telescope it just won't happen.
They arn't called faint fussies for nothing.
Like Ken said you may need to buy a few decent ep's and a UHC or Olll filter to help enhance nebula. These things take time to save for, so in the mean time there are tons and tons of things in the night sky to keep you going for years and years.
Gazz/Irish

[asimov]

I'm not sure I can agree with that totally Ken....I do to a point..12.5" newt as example.
When it's PERFECTLY collimated, it doesn't seem to matter what quality EP I bung in, weather it's a .965" Huyghenian, Ramsden or a 1.25" UO ortho I get absolutely great views! I'm talking view's that would stun you Ken..Iv'e gone to the extend of purposely putting the scope out of collimation to see what would happen to the view's using these 3 particular EPs. mentioned above.. The result was obvious straight away, Couldn't get a sharp image no matter how much I tried focusing. The 'soft' look.

Now after saying all that, I agree some EPs are total crap! I have 2 of those 500s. The view's I get through them are actually pretty sharp as long as the object is dead centre in the FOV..A lot of flare & ghosting, but if one can look THROUGH that, a pretty sharp image. Put the scope slightly out of collimation though, & it's instant crappy view. Naturally seeing & transparency etc etc all come into play as well.

Anyhow, that's my experience that Iv'e had with my particular scope...Perhaps My Parks mirror is better than what I thought! :D ?

[ballaratdragons]

John,

Maybe it's just my EP's then (Friday models). My 25mm and 15mm Series 500's have what you call the 'soft look'. Cannot focus to crisp! But my 9mm (not a Series 500) is very good. So I know it ain't the collimation. Also my 2" GS 30mm SuperView is astounding. It's just those rotton Series 500's in between! They won't focus!!

[asimov]

Oh ok. That's an established fact then. It's your EPs NOT collimation, if your getting the crisp focus with some EPs..:confuse3: That doesn't explain why I CAN get that crisp focus with the same EPs!!!!!!??????

Any theory's on why??

[RAJAH235]

A quick story. I recently purchased a *MEADE* WA 18 mm 'Chinese' eyepiece on eBay for $56.00.(Gold Coast). It duly arrived & upon unpacking it, found what looked like a nice E/Pc. taking NO notice of what was written on the box. I 1st lighted it a few days later & found that I could not get all of the image into focus. The centre was O.K. but the outer 20% was blurry/flared. Moon was absolute C**P. I tried it in another guys DOB, but it was pretty much the same. (both fast t'scopes, 4.5 & 5). When it was tried in a refractor,F7, the image was better. I put it away for the night. At home, I noticed that it said > 'ETX T'SCOPES' (OWTTE), on the box. Could I have purchased an E/Pc made for long fl t'scopes???? YEP!
It has been returned for a full refund, thankfully.
Lesson learned. :D L.

[ballaratdragons]

No John!

Maybe I just got a bad batch.
Could be my eyes too, that's something I haven't considered.

Laurie, both John and I have similiar scopes. Same EP's. Should be same images.

[RAJAH235]

After reading all this, I can honestly say the problem is......... Ken's eyes.:P
Seriously, if you're getting crisp views with some E/Pcs & not others, then I would suggest a faulty/badly made E/Pc. Maybe a lens has shifted in the E/Pc????? Have you tried anyone else's, Ken? :D L.

[ballaratdragons]

No I haven't Laurie.

I've only ever used mine. Looking forward to trying all sorts at the Star Camp.

[asimov]

Pity were so far apart, I'd love to test those 500s in mine!

[RAJAH235]

You'll get jealous!!!! S***F the new comp., give me better E/Pcs. :D L.

[ballaratdragons]

John,
I will have to take them to our observatory and test them in some other scopes. I keep forgetting.

Laurie, haha, very funny. Gimmee both!!

[ballaratdragons]

BC,

I hope you are learning something from this conversation. It could be anything, but I highly doubt that it is the scope! (unless the collimation is still out a bit)

[RAJAH235]

Yes BC. I too think your collimation may be off a little bit. As you said, if the image of 104? is not up to scratch, then I'd just be checking it out again. You didn't say what mag. you'd been up to. Is it any better at slightly higher mag? So many variables, It's a process of elimination. :D L.

[BC]

Thanks for the input folks. To clarify, I have a Bintel version, thus I got GSO EP's, the 32, 15 and 9mm. I was looking at the Sombrero with all, but the 9mm was still blurry, that obviously takes it up to 138x. The star test was a bit confusing. I could see concentric circles but couldn't tell how perfectly round they were due to the "worms" over the top of the circles (if that makes any sense).

One of my collimation probs is my use of the $29 Cheshire which is much praised on this site (I know, poor workman....). By the doco I've seen, including the one recommended in this thread, I should be sighting using the crosshairs of the tool, not the reflection of the crosshairs in the centre of the picture. My eye simply cannot focus on the crosshairs so close to my eye, even when I put on my glasses. The crosshairs don't focus until I'm about 6" away from the tool, by which time the rest of the picture through that tiny hole is useless. With my eye up to the tool, I can't see the outer edge of the focuser to see how centred the secondary is. I managed to do that by taking the 45 degree piece out of the tool. This gave me the view of the secondary I needed, but I couldn't see the cross-hairs. When I rotate the tool in the focuser, the blurred junction seems to move around. When I take out the tool and view it from the bottom end, the crosshairs appear off centre. ie if I line up the cross hairs and the pin-hole for the eye, the tool appears to be tilted. Isn't it great trying to explain technical things in words. It seems to me I need a longer sight tube with cross-hairs actually in the centre to achieve what I think I need to do.

[Starkler]

BC what you havent mentioned is how other objects look to you. Do stars focus down to a point or a tiny blob of light?
Galaxies are a challenge and require dark skies and dark adapted eyes to view well. Structure and details are faint and are usually not immediately obvious in a 10 inch scope and require a bit of eyepiece time and use of averted vision viewing the galaxy.
As Cuhullian said "They arn't called faint fussies for nothing."

In collimating my dob I dont use the crosshairs at all and have even considered cutting them out. Mine is the longer type.

If yours cannot function as a site tube just position your secondary as best you can and then adjust tilt so that you can see the reflection of the primary centred in the secondary when looking through the cheshire.

IN aligning the primary mirror you are looking to centre the mirrors centre spot in the reflected view of the ring of light from the 45 degree angled reflective part of the cheshire.

[BC]

Starkler, your description of centreing (how do you spell that??) the primary on the reflection of the secondary is pretty much how I ended up doing it, followed up by matching the cheshire reflection with the centre spot. Other things I have looked at:
Stars - kind of a point but I'm guessing
Saturn - can see the rings but no Cassini division
Jupiter - can see the 2 main bands but no other detail
Eta Carinae - can see it but is very dull. My 20x binos show it quite bright and while 40x with the scope is 4 times reduced in brighness, I imagined that the light gathering would make it a bit brighter than it is - but of course it seems my expectations were excessive. But no, I realise it would never look like the magazine piccies.
Omega Centauri - quite a lot of resolved stars
Jewel Box - quite a lot of stars and can see the orage colour in one inside the triangle
Anyway, thanks for the input - I think I just need to lower the magnification of my expectations

[Starkler]

Where do you live BC ? Maybe if you can hook with somebody more experienced they can quickly tell what is going on there.

[asimov]

BC. The cross-hair's are used to centre the diagonal, that's why some dude's centre spot the secondary, instead of guessing where the centre of the mirror is. If you can't focus on the cross-hairs, grab a dolphin torch & muck about moving the torch around at different angle's blah blah...(shine the torch in the hole in the side of the cheshire) There will come a time when the cross-hair's become fully illuminated brightly & you'll see em' easy...even though they will STILL look out of focus.

[asimov]

After thinking about what I just wrote above.....Could I be wrong about why those cross-hair's are actually there??:confuse3: Hmmmmmm..

[slice of heaven]

Is this a cheshire with the hole in the side? If so shine a red LED in the side to illuminate the crosshairs.

If the stars arent pinpoints then they aren't, no guess work needed.
Have you checked the mirrors to see if their held too tight in their cells?

If the scopes from Bintel they wouldve collimated it prior to shipping so it cant be majorly out of collimation. Only the angles of the mirrors should need adjusting.

Collimation is something you have to learn ,if someone can show you the way it'd be lot easier to understand.

[BC]

Yes it's the cheshire with the hole in the side, I'll experiment with a torch. I'm down near Canberra, I may need to chase up some helpful soul down here. I picked the scope up myself from Bintel so I know it wasn't bashed about too much on transit.

[asimov]

If it hasn't got a hole in the side, it's not called a cheshire........not in my experience anyhow...lol

[slice of heaven]

If youve seen one then your far more experienced than me, Because I havent :D

[asimov]

eh? I think weve got crossed wire's or something, lol. a cheshire has got a peep hole at the top & a hole in the side with a polished 45 deg plate with a hole in it. If it's got cross-hairs, it's called a combo cheshire & sight-tube.

A sight tube is a longer tube with the peep hole, sometimes with or without the cross-hairs...with no hole in the side or the 45 deg polished plate. OR have I got it all wrong lol......:D ps If this is wrong I'm going to blame the internet! :thumbsup:

[slice of heaven]

Its not the side hole I havent seen, its the whole cheshire. :ashamed:

[asimov]

OH! So you dont use a cheshire either.....like ME!!

[slice of heaven]

Exactly John! :D

I've a film cannister and extremely concise manual on how to collimate using a sight tube and startesting.
Definitely not recommended for beginners, I did the hard yards earlier on and now its a simple thing to do. Like you stated in one of the above posts the 'soft' image is a dead give away something is not right.

[asimov]

Your one up on me then...I dont even have a sight tube! hehehe!

[iceman]

BC, stringscope lives in canberra. I strongly suggest you PM him, or take your scope along to the next CAS meetup. They'll help you collimate it (and show you how to do it with or without tools), and they'll also be able to confirm if what you're seeing is normal (ie: yoru expectations are too high), or if there was something wrong with eyepieces or collimation or astigmatism which is affecting your views.

You'll also get the chance to look through some other types and sizes of telescopes to judge for yourself if your views are better or worse.

[stringscope]

Hi BC,

I have just read this thread. Happy to help any time. I will be at work tomorrow if you want to telephone, or send me a PM. Next CAS meeting is 21 July at Mt Stromlo. Intro Group starts at 7 PM. Topic is Cold Weather Observing. We would have time to look at your scope durig the evening.

Cheers,

[stringscope]

BC,

I have sent you a PM with ph no's.

Cheers,

[iceman]

Hi guys.

I read in another thread that BC came around to Ian's house with his Dob.

Just wondering how it went - was there anything particularly wrong with BC's dob (collimation/astigmatism), or was it just a case of expectations?

[BC]

Hi there,

I went to Ian's house last night to check things over, which was very helpful in clearing up some things for me. After all my tweakings of the adjustments, it turns out that my collimation was pretty much OK, good enough that it didn't need any adjustment last night. So it comes down to expectations I think (and EPs to a lesser extent), not helped by some quite poor seeing conditions just about the time I was getting discouraged, as well as convincing myself that I'd mucked up the colimation. I might make a comment about collimation tools though. Ian's combo cheshire/sight tube (Orion I think) made all the difference to my confidence because it is long enough to actually see the crosshairs clearly, along with the centre spot on the primary. With that tool I would be able to confidently aim the secondary, whereas the tool I was using, worked well as a cheshire, but did not work for me as a sight tube. I was surprised how well the secondary was aimed at the primary centre spot considering that I had adjusted it by visually centring the primary reflection in the secondary. I will be purchasing the longer collimation tool.

Certainly Ian's better EPs made a difference, which gives me a good idea of what I might expect for a price, but it also shows that my GSO ones are quite acceptable for the time being. Ian had his modified 8" f/6 set up as well as his stringscope (which is a very clever piece of equipment) so that gave me an idea of what is "normal". We looked at plenty of DSOs from his place in the suburbs with good success (even a monthly challenge object). All in all a very informative evening and very good to have my expectations "normalised" and stop worrying that my scope is not OK. My little exercise in doubt demonstrates clearly why it is good to look through other's scopes before you buy, something that is constantly advised, but just didn't work out for me at the time. (gotta have a scope !!)

So a big thanks to Ian as well as the folks here who contributed thoughts along the way. Now with a fresh attitude, bring on the night....

[iceman]

Well done BC and well done Ian, great to have that experience under your belt. A fresh look on things will rejuvinate you!

[slice of heaven]

Whew. For a while there BC I thought you might walk the plank.
Great to hear your on track now :thumbsup:

Good point you've raised on collimation tools. As with most things, you get what you pay for. Though the cheshire from Andrews is recommended a lot here(because of the price), its not the be all and end all of collimation tools. Theres a vast array of tools available, from the cheap and better than nothing.....up to the expensive and well worthwhile. Each tool has a drawback and more often than not 2 tools are required, one to remove the errors of the other. Do some research on the tools available and grab a well designed and highly recommended unit.