Advice needed!

[Surreal]

Hi All,

I stumbled onto this forum 2 nights ago, fantastic forum that kept my up till 2am reading past post!

Anyway I was dead set on getting a 10" dob from YorkOptical here in Melbourne, and take advantage of the 20% off, but being the 37 degree day that it was, I didn't end up going down there, and now the prices seem to have gone up on the website!!

The 10" is now $949 and the 8" is $599, I'm tempted to be patience and wait it out, do some more research, go back to playing with Strellarium and my binoculars, cause thing appear to have gone out of the budget I had set. What to do!

Anyway I had a few questions now.

1. Is the 10" dob easy to move around or is the 8" dob more the go if I was going to be moving it around abit?

2. Somewhere down the track I intend to change the mount and hook my Canon 450d onto it. All that I've worked out so far is that some sort of camera attachment ring is needed. So then what happens? Camera attaches onto lens of choice, which attaches onto attachment ring which attaches onto telescope?

3. I live almost towards the edge of the western suburbs of Melbourne and the sky is not exactly dark at night. I've seen the planets from telescopes in my area, but am I going to see deep space objects in these conditions with the telescope I intend to buy?

4. That is going to sound silly, but what is the moon filter for? Do you need one when viewing the moon? I've taken some lovely pictures of the moon from my 450d with the zoom lens

Your thoughts?

Surreal

[Octane]

Surreal,

:welcome: to IceInSpace, the best web site in the world! :D

1. Either should be easy to move around. It's when you start getting into 12" aperture and above, that it can become tricky -- especially transport;
2. What you do is attach a T-ring on to your camera (these can be had for around $40) and a camera adapter barrel, which then slides into the focuser. This is called prime focus imaging. The other way of doing things is attaching a camera (with lens) on top of your telescope whilst it's on the mount. This is a piggyback configuration;
3. You should be able to see some detail, but, for maximum impact, you will need to travel out to a dark site. Check out the star parties forum to see if there's a society nearby you that you can attend. They'd love to have you along;
4. No such thing as a silly question -- just silly people! Just kidding! :poke: A moon filter is a neutral density filter. The purpose of it is to tone down the bright eye attack that the Moon is through an eyepiece. It also helps to add contrast and allows you to see finer detail.

I hope this helps.

Enjoy your stay. :)

Regards,
Humayun

[Surreal]

Thanks Humayun! :)

I went down to York today, and the 10inch is huge! I think im now set on the 8", since I think it will be more portable and I'll get a whole lot of use out of it. Didn't have my car and had to get back to work, otherwise I would have brought it right there and then.

Some other questions I have.

1. What would constitute as a good eye piece? Is it brand? Is there a place I can read reviews like how I do with SLR lenses for my camera before I purchase?

2. There seems to be a couple of different collimation tools about. Is there a recommended one?

Thanks!

[erick]

Hi Surreal

Western Suburbs eh? Just down the road from me. I'm happy for you to get in touch and I can show you some things - easier than trying to write them down, I assure you. Eyepieces, collimation tools etc.

Yep, an 8" scope will get you started and you'll learn a lot.

You'll soon discover Melbourne skies are Yuck for any serious viewing of fainter interesting objects. But the Moon, the planets, stars are fine. The brighter objects like 47Tuc, M42 can be seen.

I head for Snake Valley (south-west of Ballarat) when I have the time and want really dark skies.

Eric :)

[gman]

I have a VX commodore and a 10" dob fits ascross the back seat and the base/mount fits in the boot.

[acropolite]

FWIW York Optical are offering discounts (http://www.yorkoptical.com.au/ShoppingCart/IceInSpace/tabid/988/Default.aspx)to IIS members for on line orders.

[Surreal]

Thanks Erick, yup down the road, a good 30mins down the road! but I may take you up on that offer. Snake valley sounds interesting, I've had a look at the Snake Valley Astronomical Association website a few nights ago. (along with the other associations in Melbourne)

Acropolite - Thanks, I've been down to York to have a look at their scopes yesterday.

Doing some more research, but can someone confirm my gut feeling that the bintel 8inch dob deal is a better deal than the skywatcher. Details are

Bintel 8inch dob $699 - includes 26mm (2") Fully Multi Coated Eyepiece, 15mm and 9mm Fully Multi Coated Plossl Eyepieces, Moon filter, 8x50 90° Correct Image Finderscope, crayford 10:1

Skywatcher 8inch dob $509 (after 15% off IIS deal) - Rack and Pinion focus system, 2 EP (1.25” Super 25 and 10*)

Thanks,
Surreal

[rastis95]

Never seen a skywatcher dob but i own a 12" bintel dob and haven't been able to fault it, plus they don't mind if you hound them with questions.
Cheers
Scott:D

[erick]

You'll enjoy the 10:1 Crayford over a rack and pinion. You might find the right angle correct image finderscope to your liking - many do.

After that, an extra eyepiece - the GSO 15mm plossl is useful - and a moon filter - good to have but cheap to buy.

The 2" eyepiece with the Bintel gives you experience of this size eyepiece - expect to end up with some 2" and some 1.25" eyepieces. Some people stick to 1.25" throughout, but not many.

Is it worth an extra $190? Your call!

[bmitchell82]

I can say if your going to go the astro photography way, a 8 Inch is ample sufficent! ive seen some lovely shots taken though a 8" dob mounted on a Eq6 pro.

I myself went the 10" just for that extra light grab. and plus it can fit into the mitsi lancer with ease (enough for my miss's, son, myself plus heaps of other gear)

Dont be affraid of the 10" its only marginally wider than the 8", they both have the same focal length, that is 1200mm, and if you go though my posts youll see that i did a semi review on the sw 10". Just depends on what you want to do, ask yourself this question as it will save you dollars at the end of the day.

Astro photography, CCD's DSLR's are sensitive to light, you don't need aperature.
very very sturdy mount capable and future proof

Visual astronomy, eyes are gay! :) the biggest badest mirror you can get your hands on.

If you live in dark skies, dobs are just as good as go to's if you live in metro, goto is the only way! there are no stars to star hop!:thumbsup:

[CB]

Hi Surreal,
In regards to astrophotography.
I have gone down this path with an 8" saxon on a HEQ5 GoTo mount and am getting some great photos.
BUT....you can't just get a t-ring for your camera and mount it in the focuser because there is not enought inward focus.
Want you have to do is purcase a low profile crayford focuser 10:1 ($160 approx) to give you focus but then to use your eps you need an extension tube to regain focus.
Or.....move the primary mirror up the tube to compensate for the inward movement of your camera. There is a link in projects & articles that explains what it do in detail. I went the low profile way.
Cheers
Chris

[bmitchell82]

mmmm so that nose piece is different yeah? that sucks.! because on the standard SW newt theres two adaptors one for the 1.25 and 2" the 1.25 has a screw in nose piece, you can take that out and it gives heaps of focus on the SW. ahhh well.. you win some you lose some!

[Surreal]

Eric - Worth the extra $190 is a good question. I hope I can answer that when I go down to bintel to have a look in the next few days. Knowing myself I probably will end up picking up bits and pieces anyway and it will work out more expensive in the longer term if i took the skywatcher

Is there a advantage or disadvantage of the 2" EP over the 1.25" EP?

Brendan - Thanks for the advise. I'll need to take a look at the 10inch again, my initial thoughts were "woah! BIG!", I won't even tell you my reaction to the 12inch next to it!

Chris - Does the low profile crayford affect normal viewing? Does it absolutely have to be a low profile focuser or does a normal crayford focuser do an ok job in some situations without the moving of the primary mirror?

Thanks for all your help everyone! I'm loving this forum!

[erick]

Nothing in particular. You'd sort of expect that longer focal lengths would be in wider barrels, but that isn't always the case - depends on eyepiece style and apparent field of view. Televue's 40mm plossl is 1.25". You'd think the Ethos 13mm with a whopping 100 deg AFOV would need a 2" barrel, but, no, 1.25" does the job (but it has a 2" skirt for convenience). The 17mm Ethos has a 2" barrel, 1.25" doesn't cut it I guess.

In general, 2" eyepieces are bigger and heavier when it comes to storage and handling. 2" eyepieces mean no additional adapter needed in your 2" focusser to work loose or wobble around. But that doesn't seem to be much of a problem either.

[CB]

Hi Surreal,
These photos might help explain what I mean. Both are the same low profile focuser on my scope.
Fig 1 is with the camera adapter on and fig 2 is with the extension tube required to bring it back to were a standard crayford focuser would be were the eye piece would work. Note the difference in height, this is the inward focus you need for a DSLR.
OR... you can move the mirror up the tube...good for camera but you will still need an extension tube for your eye piece because you will have shortened focal lengh of your scope. That is the idea of the low profile unit (shorten the FL) based on a 1200mm FL
Hope this makes sense.
Cheers
Chris

[bmitchell82]

Okay wize sages i would like your knowledge base brains trust why can a cannon 350d reach prime focus with the standard SW focuser and any other cam cant? im baffled!

[CB]

OK lets start.
What is the aperture and focal lengh of your scope ?
Chris

[Zuts]

The focussed image is formed on the CCD. The only variable is the chip distance. Any camera (or piece of wood) with a chip the same distance from the front of the camera will also come to focus.

Maybe you are right on the margin with the 350 D, so other cameras need more in/out focus. However any Canon camera should work.

Cheers
Paul

[Surreal]

Thanks for everyone's help. I picked up a 8" dob from Bintel today! It was the last one on the floor, so i was offered a discount or some free stuff. It was going to be another 4 weeks till they get more stock in cause of chinese new year. Can't wait to get out there tonight and have a play around. I'M EXCITED!! :lol:

Not sure if I understand this camera to telescope thing yet. But i figured i probably want to try it out so i got the adapter for it. I guess i'll find out if I need the low profile crayford. It seems to have one end that twist out to allow an EP or something like that.

I'm trying to find all the links on how to collimate, and you know when you go to find something when you need it, you can't find it! If anyone can help me out with some good easy to follow links on collimating the dob, it would be much appreciated!

Surreal

[Surreal]

Nevermind about the collimate, After a few moments screwing and unscrewing, I understand now! Let me see if this is right.

1. You first check the secondary mirror through the focuser to see that it's in the center, and at the correct angle facing the you as you look through.

2. Put in laser collimator. You get the laser to go to the center of the primary mirror by lossening all 3 screws, then tightening the one that closers to where the dot is. It is essentially a tighten two screws, and losen one to put the secondary mirror at the right angle so that the dot is at the centre.

3. You adjust the knobs at the bottom to have laser enter the collimator at the exact same spot using the same method as number step 2.

Did i understand that right?

Surreal

[rmcpb]

That is your basic collimation and will work well if your laser collimator is collimated itself.