ICEINSPACE
Moon Phase
CURRENT MOON
Waxing Crescent 12.6%
|
|

08-11-2009, 01:15 PM
|
Neo - as in Dr Neo Cortex
|
|
Join Date: Dec 2005
Location: Mt Druitt
Posts: 205
|
|
What Scope/Mount for A Canon EOS
Hi People,
I currently use a Bintel BT-252 Dob. I purchased this some 5 years or so ago. The primary mirror is a little worse for wear, and will be replacing that shortly.
However, having said that, I am now interested in astrophotography, especially DSO's, and a Dob, with my new camera ( Canon EOS 1000D with a 55 and 300mm lens ) is not going to cut it. Not without an EQ6 mount at least.
Having said that, I have spent quite a few days, searching around the web for scopes that would suit this camera, and have literally hundreds of differing answers.
No way I will give up my Dob. I understand it is primarily a low cost scope, which was ideal given my circumstances at the time, and still is for "visual" viewing.
I even added an Argo Navis to it ( that was a bummer - the encoder steps were always just that little bit out - I have never been happy with it).
SO guys, your experience is required:
1. Scope/Mount - say up to $2500 - Equitorial or ALT/AZ with autoguiding and goto?
2. Adaptor Rings, any correctors I would need for Coma, etc
Something from the Andrews or Bintel catalogs would be ideal.
I've had a look at a few EBooks on the subject, but again, so many varying opinions. Yes, astrophotography is not for the faint hearted
Cheers
DOC
|

08-11-2009, 03:14 PM
|
 |
Refracted
|
|
Join Date: Sep 2007
Location: Carindale
Posts: 1,178
|
|
I'm sure you will get lots of answers so I won't attempt to cover all of your questions, but do have a few comments.
Due to the high pixel density of DSLRs, their best match is to optics of, say, 1200mm or less focal length. Beyond that focal length and you are over-sampling unless you use focal reducers. Beyond about 2000mm focal length you will lose your ability to effectively use most focal reducers.
For your budget I'd personally recommend a 150 to 200mm aperture newtonian, or a 80-100mm apo refractor if you want to take the less stressful road. Examples are https://www.bintelshop.com.au/Product.aspx?ID=8471 for the newt and mount, or the same mount with an ED80 or similar refractor on top. For the newt you would need a coma corrector. For the refractor you would want a field flattener. Note that this size of refractor will not give good results with smaller DSOs, such as planetary nebula, and is more of a wide field configuration. However, it is much more forgiving than a newtonian or SCT would be to learn on.
If you want to do guiding using a second OTA, you'd be needing either a side by side or piggyback setup for the guide scope, plus a guide camera, plus the guide scope. Realistically adding guiding of this type will add $750-1000 to the cost of the setup as a result, and also can push the weight limits of the mount.
Regards,
Eric
|

08-11-2009, 04:15 PM
|
Neo - as in Dr Neo Cortex
|
|
Join Date: Dec 2005
Location: Mt Druitt
Posts: 205
|
|
Hi Eric,
Many thanks for the info. I checked out the Bintel link you provided, and the first thing that struck me was that I wouldn't have to "cut" my scope to obtain focus.
That was probably the main reason I was hesitatant with going for a newt, that and the weight!. Personally, no way I could get vibration free long exposure shots with that sort of wieght on an EQ5 with my current scope.
If I can get a reasonable 8", with goto, etc, for under a few grand, hell, thats a good deal. A good compromise, visual and photography.
My guess is that field rotation won't be a problem here ?
As for my 10" - if I can actually get the best of both worlds, I'll donate the 10" to the local school. 5 years old, with piting, but, hell, still better than nothing, and perhaps some kids will get the same sense of awe I still get.
The biggest drawback I can see, is like all newts, collimation ( pretty well have that down pat now ), and portability. I intend to leave it in the backyard ( light pollution galore ), but if your not going away for a weekend, or such, the setup time can be exhausting.
Again, many thanks for the info - I was actually looking at an EQ6 mount, and that was going to set me back even more, as for portability - forget it!
My other option is one of the Orion ED series.
Keep those replies rolling in people - the more info, the better my decision.
Cheers
DOC
|

08-11-2009, 04:33 PM
|
 |
daniel
|
|
Join Date: Sep 2007
Location: Macedon shire, Australia
Posts: 3,427
|
|
DOC those newts should be designed with both visual & photography in mind..they either come with a screw off focuser extension or an extension tube - allowing you to do both..although the focuser isn't particularly strong anyway
|

08-11-2009, 05:05 PM
|
Neo - as in Dr Neo Cortex
|
|
Join Date: Dec 2005
Location: Mt Druitt
Posts: 205
|
|
Hi Dannat,
I'm beggining to think, that perhaps I should simply replace my primary, and get a goto mount to suit the BT-252. What I love about these, is they can take a lot of punsihment ( not intentional of course  )
It gets back to the weight of the whole thing, I can imagine what that would do for long exposure images.
Am I going to get the best out of both worlds, or am I better keeping my Dob, and looking for a totally new scope for photography.
Hell, if I get pi**ed, I can always take a look at Orion through my 10" for some sanity
Right now, sick of reading, and I need people with practical experience in this subjsect, to perhaps point where I should be.
Cheers
DOC
|

08-11-2009, 06:10 PM
|
Registered User
|
|
Join Date: Feb 2007
Location: Beaumont Hills NSW
Posts: 2,900
|
|
If you have photography in mind I would suggest that you put the money into a good mount like an Eq6 which is reasonably priced at the moment or even a G11 if you can afford it. I just got a G11 they are under $5000 at the moment complete with Gemini
Put your Camera on the equatorial mount and practice wide angle shots and stacking. You will need a computer (Laptop) and some free programs like PHD and DSS. You will be surprised at the results. My son put his 1000D on an ETX125 and took lots of 50 second subs that gave fantastic results.
When you get proficient at this you will know what sort of an OTA to get for the serious DSO's including an auto guider.
Barry
|

08-11-2009, 07:30 PM
|
Registered User
|
|
Join Date: Jan 2007
Location: Gateshead
Posts: 2,205
|
|
Keep the OTA and do some upgrades :
- if the primary is in need of recoating , send it away to be done.
(might just be dusty / dirty , that's easy fixed)
- if it's got a 1.25" rack and pinion focusor , get rid of the focusor and buy a nice 2" low profile crayford focusor
- rings , check the tube size (outside diameter of the OTA) and ask the local dealers if they have a set of rings + dovetail + spacers to suit, if they don't , contact Orion Optical in the UK, they'll be only too happy make a set of rings for your scope
- GEM (you wont get much of GEM or one that's going much good for astrophotography with a 10" (f5 ?) for the kind of money you mention , not brandnew anyway ., since Lumicon no longer make their esyguider compatible coma correctors , you'll need a guide scope with similar focal length as the newt to mount side by side or piggy back (so you'll need a capable GEM.
A G11 may be a bit undersized.
I'd suggest you keep any eye on the classfies here , at CN and other places for a good capable 2nd hand GEM , it need not be GOTO, as it's not likely that the prices asked by the local retailors will fall in line with the improved value against the USD and JapYen.
They've lots of old stock that they bought when the dollar was poor that they'll have problems shifting now .
|

08-11-2009, 09:07 PM
|
Neo - as in Dr Neo Cortex
|
|
Join Date: Dec 2005
Location: Mt Druitt
Posts: 205
|
|
Hi Ian,
It's an f5, an f 4.5 if I cut it to ribbons  . I have removed the primary a few times, distilled water, etc. My fault, I let the elements in once or twice.
The BT-252 comes standard with a 2" Crawford, not the smaller.
It really comes down to keeping this scope, which I doubt is worth it, considering a new mirror in comparision to the cost of the whole scope.
Thats what the GSO's are famous for, bang for buck, and the aperture/mirror, is your bang with newtonians.
I liked Barrys ( earlier post ) comment. If his son can shoot away dozens of frames on a more forgiving scope, perhaps the way to go. Then Erics comment re the 8" refractor - viewing/goto/photo/all in one for less than $2,000, allthough I wonder how good those shots would be given that's an 8" on an EQ5 - calculate the extra weight, and those gears, hmmmm.
Now you can see exactly where I lie - there really dosn't seem to be an agreed good starting point.
f/5 - seems to cover most objects, but, for value, you could really only go a newt with that ratio.
Is there a "forgiving" setup, keep my Dob, and still buy something in the 2-3,000 range ? Like I said the ED series.
Ciao
DOC
|

09-11-2009, 08:07 AM
|
Registered User
|
|
Join Date: Jun 2006
Location: pittsburgh pa
Posts: 268
|
|
i think for DSLR, ED's or APO's (F7 or faster) are nice, also i like SCT's with a reducer- whats nice about an SCT is the focus travel is tremendous, i never cared for imaging with a newt due to possible focus issues, and the problematic mounting of the camera position
|

09-11-2009, 07:36 PM
|
 |
Newtonian power! Love it!
|
|
Join Date: Jul 2008
Location: Mandurah
Posts: 2,597
|
|
I run a 10"dob with everything mounted on the eq6 the images you can see in my web site below.
AlexN runs with the heq5 and a 90mm apo which is great wide field of view.
depends on what you want out of the scope. btw you can buy replacement mirrors from GSO for a few hundred if your mirror is fubar!
In anycase the GEM mounted dob will give you the bang for buck with aperature being the key point a upgraded focuser is a must for photography! good luck!
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT +10. The time is now 02:18 PM.
|
|