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Old 09-12-2011, 02:53 PM
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Gso rc10

I am thinking of getting a CF 10" RC for imaging with my AO-8/CFW8/ST2000xm/Losmandy G11G but I have some concerns and would appreciate some advice before I take the plunge.

1. Is this setup a good combiation for DSO imaging? I am in semi dark skies - the outer suburbs of Sydney - can see the Mway on a no moon night quite well...

2. Is the stock 3" focuser sufficient or should I plan on upgrading it
immediately? Will I need to refocus on filter changes - even if my filters claim to be parfocal? If the CF tube stable thermally such that I will not need to refocus due to thermal effects? Typical dusk/dawn delta T is 10C in my location.

3. I am not mechanically adept and am concerned about a couple of issus with this design of scope - the inital setup/collimation (I can ask the supplier to do that). But ongoing how frequently will collimation need to be tweaked? Not to happy with the idea of having to shim focusers or tune mirror separation. Are these scopes set/forget of in need of regular care and attention?

4. Will I need a FF given my ccd is not too large and if yes which unit is
recommended?

5. I beleive these units have plenty of backfocus - so my imaging train should be ok - true? Would the FF make any difference?

Is there a better option for the money? I have had a VC200L in the past and was not overly impressed with it, but need a bit more light gathering power than the ED127 I am using today.
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Old 09-12-2011, 05:35 PM
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1.RC's are good for DSO's they are zoomed in so your hunting small details out of larger nebula or galaxies generally. As for the tube shrinkage you should refocus during the night its best practice other wise things can happen.....

2. You need a different focuser it wont be sufficient for hanging that kind of kit off the back.

3. Like all mirrored optics they require tuning and adjustments if that scares you don't get a RC because they are notoriusly sensitive to miss collimation errors aka, if you do take it to a reputable dealer then the trip home may put it out of colimation again.... Plus you really need to do it under the stars i would suggest that it will cost you a pretty penny for them to do it!

4. FF no you shouldn't need a field flattener but it never goes astray!

5. Sorry you have to measure the total back focus your kit requires then look at what is stated as the back focus given for the RC10.

6.Is there a better option? well it really depends on what you want to take photos of.... match the telescope to what you like to image with plus your skill plus your wallet

Brendan.


Quote:
Originally Posted by JohnH View Post
I am thinking of getting a CF 10" RC for imaging with my AO-8/CFW8/ST2000xm/Losmandy G11G but I have some concerns and would appreciate some advice before I take the plunge.

1. Is this setup a good combiation for DSO imaging? I am in semi dark skies - the outer suburbs of Sydney - can see the Mway on a no moon night quite well...

2. Is the stock 3" focuser sufficient or should I plan on upgrading it
immediately? Will I need to refocus on filter changes - even if my filters claim to be parfocal? If the CF tube stable thermally such that I will not need to refocus due to thermal effects? Typical dusk/dawn delta T is 10C in my location.

3. I am not mechanically adept and am concerned about a couple of issus with this design of scope - the inital setup/collimation (I can ask the supplier to do that). But ongoing how frequently will collimation need to be tweaked? Not to happy with the idea of having to shim focusers or tune mirror separation. Are these scopes set/forget of in need of regular care and attention?

4. Will I need a FF given my ccd is not too large and if yes which unit is
recommended?

5. I beleive these units have plenty of backfocus - so my imaging train should be ok - true? Would the FF make any difference?



Is there a better option for the money? I have had a VC200L in the past and was not overly impressed with it, but need a bit more light gathering power than the ED127 I am using today.
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Old 09-12-2011, 05:52 PM
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Good advice from Brendan.

Overall that would be a good setup. I am not sure how well these scopes hold collimation but if handled carefully I would like to think it would retain collimation. My experience with that is with Tak or RCOS scopes.

I found them to hold their collimation really well. I would drive to my dark site 4 hours and back many times and their collimation was spot on for ages. GSO RC though won't be as well made but there are plenty using them. If you simply take inside and take it outside it should be fine.

There are threads on this site about these scopes. The only other item would be reflections. I believe the scope needs the main baffle flocked.
See Paul Haese's thread about how to do this or PM him as he has a lot of experience with this scope.

Setup right these scopes are awesome. Look at Leo's images in deep sky forum. Fabulous.

Greg.
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Old 11-12-2011, 09:28 PM
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Quote:
Originally Posted by JohnH View Post
I am thinking of getting a CF 10" RC for imaging with my AO-8/CFW8/ST2000xm/Losmandy G11G but I have some concerns and would appreciate some advice before I take the plunge.

1. Is this setup a good combiation for DSO imaging? I am in semi dark skies - the outer suburbs of Sydney - can see the Mway on a no moon night quite well...

2. Is the stock 3" focuser sufficient or should I plan on upgrading it
immediately? Will I need to refocus on filter changes - even if my filters claim to be parfocal? If the CF tube stable thermally such that I will not need to refocus due to thermal effects? Typical dusk/dawn delta T is 10C in my location.

3. I am not mechanically adept and am concerned about a couple of issus with this design of scope - the inital setup/collimation (I can ask the supplier to do that). But ongoing how frequently will collimation need to be tweaked? Not to happy with the idea of having to shim focusers or tune mirror separation. Are these scopes set/forget of in need of regular care and attention?

4. Will I need a FF given my ccd is not too large and if yes which unit is
recommended?

5. I beleive these units have plenty of backfocus - so my imaging train should be ok - true? Would the FF make any difference?

Is there a better option for the money? I have had a VC200L in the past and was not overly impressed with it, but need a bit more light gathering power than the ED127 I am using today.
1. I have just purchased my GSO RC10CF and I am getting things ironed out to get the best of it. I am in the suburbs of Perth and I can get very good pics even with light pollution in the area.

2. The stock focuser has been improved in the latest models and if all you were using was a DSLR it would be fine. Heavier imaging trains need the change over to better focusers. The choices range from Atlas and the like (sell a kidney but worth every penny) to Feathertouch (expensive when optioned up built like a brick s***house and ultra reliable, a standard option at many overseas sales sites like altair astro!) or there is moonlight (well made cost effective <$500 for fully motorised, well respected all round).
refocusing on filter changes etc will depend on your filters. Checking focus after hours of imaging is good practice. I've only had my RC10CF for a short while and I have not had to refocus all night as when I checked it had held for the entire time. I have not had it over winter where my C9.95 seemed to change every couple of hours.

3. Collimation is a biggy here for RC scopes and needs careful attention as they are really picky. There are a number of threads here and the ultimate answer is the TAK collimation scope be aware that it's 2.7" and you will need adapters to suit. You can collimate without the TAK scope and there are a number of guides to help, please read the forum posts as some of them are very helpful but 'BACKWARDS!!' can get very confusing when following the guide and it's getting worse not better. Once collimated they hold well but the usual cavet applies to rough handling.

4 & 5. They still can use a FF and I am running the Astrotech 2" FF which works well with these scopes. It's 2" so if you go the wider route (2.7" etc) this won't be any good for you. Greg mentioned LEO's pics and they are indeed really good. He has a slightly slightly smaller chip and he uses the Astro Physics CCD tele compressor CCDT67 - 0.67x Reducer http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4955_Astro-Physics-CCDT67-0-67x-Reducer-2----e-g--for-GSO-RC.html
this has a 22mm full circle at 0.67 reduction at 101mm. I use a QHY10 which is a full APS sized chip so this combination would give me viginetting. There is another suitable FF reducer from astro physics but it's number escapes me. Ricks is using it on his RC and it's a 2.7" connection.

Set up right there are many good pics from these scopes. Greg mentioned reflections in the baffel tube but this was supposed to have been addressed in the new models and I have not seen it with mine yet. Paul Hase had one of the earlier models and there is a comprehensive guide on his web site on how to flock the tube. As Brendan said these have a narrow field of view and are for giving detail or hunting out small targets. This can be improved with the FF/FR as in the case of Leo's pics.

All up I'm happy with my one even though the weather gods have punished me mightily for buying it!!


Good luck

Paul
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Old 11-12-2011, 09:48 PM
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Quote:
Originally Posted by ReaPerMan View Post
There is another suitable FF reducer from astro physics but it's number escapes me. Ricks is using it on his RC and it's a 2.7" connection.
I'm using the 27TVPH 0.75x reducer from Astro-Physics.

I'm also pretty happy with my RC10 but still working out how to get the best out of it. If the weather ever improves I'll be testing out a new imaging train with an Atlas focuser and Starlight Xpress AO-LF active optics unit...

Cheers,
Rick.
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Old 11-12-2011, 10:23 PM
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Agree with all written before me.

Three comments really.

I have the 12" now as well as the 8". The 12" shows no reflections at all even with the STL11K sensor. Field looks pretty flat too. There are lots of great images taken with the 10" and as has been pointed out Leo's images are superb. The baffles seem fine now generally. That means not having to pull it apart.

The collimation of these scopes is a little tricky but not impossible. Owning a folded design telescope always means being able to collimate correctly. It can be daunting at first but once you get into doing this regularly you will not look back. Try to get someone to show you how to collimate.

I have bought a focusor as a matter of course. The new focusors look ok but I want total reliability so prefer just to spend the money on the focusor. My recommendation is to do the same with the rig you want the focusor to support.
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Old 12-12-2011, 11:36 AM
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Thanks for all the feedback. I am pretty sure I will go for a 10" with the AP CCDT67 reducer (my CCD is not to large) and an uprated focuser - probably a moonlite as I have had their kit before and liked it.

I do not think I want to go for the Tak collimation scope straight off..seems a bit of a costly option. What is the next best option?
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Old 12-12-2011, 12:45 PM
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I have the Tak scope but am trying the "hall of mirrors" method to collimate
and that should get you very close - see here http://www.davidcortner.com/slowblog/20110815c.php
Then its a matter of doing a star test to fine tune it.
Bobs knobs are also now available for the RC as well.

Mark
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Old 12-12-2011, 05:33 PM
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Rick,

I am curious - can you use the FR and AO unit together and still get the CCD spacing right? What is your imaging train exactly? I was not planning on the 27TPH - rather the CCDT67 as my ccd is smallish and will work with the greater FR that gives BUT I am not sure about spacing with a CFW8 and potentially, an AO-8, in line.

Regards,

John

Quote:
Originally Posted by RickS View Post
I'm using the 27TVPH 0.75x reducer from Astro-Physics.

I'm also pretty happy with my RC10 but still working out how to get the best out of it. If the weather ever improves I'll be testing out a new imaging train with an Atlas focuser and Starlight Xpress AO-LF active optics unit...

Cheers,
Rick.
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Old 13-12-2011, 05:31 PM
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Quote:
Originally Posted by Marke View Post
I have the Tak scope but am trying the "hall of mirrors" method to collimate
and that should get you very close - see here http://www.davidcortner.com/slowblog/20110815c.php
Then its a matter of doing a star test to fine tune it.
Bobs knobs are also now available for the RC as well.

Mark
Thanks for the Link Mark, that was a very useful process that was revealed in the blog as well as some great pictures taken with the RC10. I was impressed, so I have bought the extra piece of kit that was mentioned,

http://www.teleskop-express.de/shop/...and-Astro.html

This might help me along with the bob's knobs that I have coming.

Cheers

Paul
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Old 13-12-2011, 05:40 PM
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No prob Paul , I am holding off getting that adjuster untill I have collimation
spot on and then see if I have tilt but so far it looks pretty good across the CCD . Does show how good the images can be if you take time to get it well collimated

Mark
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Old 13-12-2011, 07:15 PM
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John,

One reason I picked the 27TVPH instead of the CCDT67 was the longer focal length (700mm vs 305mm) which provides a bit more room for an AO unit. If you haven't found it already, there's some technical info and example spacing calculations on the 27TVPH and CCDT67 here: http://www.astro-physics.com/tech_su...r-techdata.pdf

My image train is: RC10, Atlas focuser, [optional 27TVPH], AO-LF, SX filter wheel, SX OAG, SX H18 camera.

My spacing between the FR and CCD focal plane is fine. My only concern is total back focus distance. I haven't proved I can reach focus with the FR and AO combined yet. It will be very close with my current set of off-the-shelf adapters. If I can't get there then I'm certain I will be able to with a custom adapter from 2.7" to 72mm which will replace three separate adapters between the FR and the AO unit. I just need a clear night to check my current configuration...

Cheers,
Rick.

Quote:
Originally Posted by JohnH View Post
Rick,

I am curious - can you use the FR and AO unit together and still get the CCD spacing right? What is your imaging train exactly? I was not planning on the 27TPH - rather the CCDT67 as my ccd is smallish and will work with the greater FR that gives BUT I am not sure about spacing with a CFW8 and potentially, an AO-8, in line.

Regards,

John
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Old 13-12-2011, 09:03 PM
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RC10 and FR

Thanks Rick,

I only have a small format ccd and 1.25" filters - so the 2.7" FR would be overkill and also mean I would have to go for a feathertouch or similar 2.7" or bigger focuser - which more cost than I can take for now.

If I have my calculations right the CCDT67 will still be useable with the AO-8 in line but it will give less than a .67 reduction as the separation will be > 100mm, a good rather than bad from a coverage pov. I believe total back focus will not be an issue as I intend on purchasing the new Moonlite 2.5" CFL unit that has just been released - this allows the FR to be fitted inside the draw tube and separation finely adjusted - pretty good I think.

The only item I need to decide on now is the tube - I was going for CF but as I am going to go for a motorised focuser it would seem I may as well stick to Al, are there any other reasons than cosmentic to stick with the CF tube eg total weight, better rigidity/thermal stability?

Finally is there any need to worry about dewing with these units and, if yes, how do you deal with it - dew shield? heaters (if yes where)?
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Old 02-01-2012, 05:29 PM
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Took the plunge - RC10CF 1st light...

OK so the recent poor weather was, at least in part, my fault, sorry. I have a shiny new scope and had a clear night without conflicting commitments so I gave it a go on Eta Carina. Yes, I know, sorry, but it is a useful calibration target as I have imaged it with my previous setup and can compare/contrast. I also looked through it - and it gave me a good view of Jupiter, nice and sharp and bright.

Unfortunately I blew my ST2k on my first attept to image with this scope (comets ARE bad luck!) so I have had to use my unmodded Canon 20D which is not a great match to the OTA but never mind. Attached is my first effort (no flats - 10*4 mins @ ISO 800)

For those who know these scopes I would appreciate your feedback - I think my focus was a bit soft, but close (no live focus on the 20D and my Moonlite is still in the post). I see some field curvature in the corners - that wil not hurt with the ST2k which has a smaller chip but is this normal? In the bottom left corner the bright stars have sprouted and extra pair of diffraction spikes which is odd.

I have also attached a view of a defocused star - I think it is showing collimation to be good - but is it great?

Thanks for any and all feedback.

Oh and yes I am happy with the scope - just itching to get the ST2k on it....
Attached Thumbnails
Click for full-size image (eta_small.jpg)
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Click for full-size image (RC10CF.jpg)
158.0 KB126 views
Click for full-size image (RC10-Coll.jpg)
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Old 02-01-2012, 06:08 PM
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Looks like you are on the right track. Collimation looks pretty good, but the defocused star is a little big to be really sure of collimation. Something about half that size will be more accurate.

Field curvature is normal for RC telescopes and like you said it will be less evident with the smaller sensor. I can be sorted with flatteners and reducers too.

The eta image looks sharp the detail looks as it should. You can compare your images to my eta image with the RC8 and a 40D if you like.

I look forward to more images coming from you.
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Old 02-01-2012, 08:28 PM
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How did you blow up the ST2K?
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Old 02-01-2012, 10:50 PM
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Surely you would have to be happy with Eta Carina. I have thought of these scopes as well and my concern is the back heavy nature of these scopes. Is this an issue with balancing and also do you think it would go OK on an EQ6Pro and also how do you find the mini guide scope?? Lots of questions. Sorry.

Mark
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Old 03-01-2012, 10:28 AM
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Balance of the scope is not an issue. Generally you will find that the rings or dove tail will be right near the rear of the mirror cell, but balance can be achieved easily.
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Old 03-01-2012, 11:47 AM
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St2k

Hi Terry,

My sorry tale is here:

http://www.iceinspace.com.au/forum/s...ad.php?t=84942

Bottom line is that my power supply was faulty.



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How did you blow up the ST2K?
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Old 03-01-2012, 11:59 AM
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Quote:
Originally Posted by batema View Post
Surely you would have to be happy with Eta Carina. I have thought of these scopes as well and my concern is the back heavy nature of these scopes. Is this an issue with balancing and also do you think it would go OK on an EQ6Pro and also how do you find the mini guide scope?? Lots of questions. Sorry.

Mark
Hi Mark - yes I saw those issues too - lots of extensions and kit hanging wayyyy out the back - it did not look stable. But that was with the RC8. With the 10" I am in focus with the standard focuser and no extensions using a 2" diagonal and EP or with an OAG with my 20D or with my SBIG train (Ao-8, CFW8, ST2K). Also 3 x 2.7" diameter extension pieces are supplied so, if you need to, you can extend using a rigid mounting system. That said the stock focuser supplied was truely awful (Bintel swapped it for me and the replacement is ok) so an upgrade should be budgeeted for (my Moonlite should be hee soon!)

As for balance - yes it is almost all the way forward on the dovetail rail but it does balance ok (I do use 2x21 lbs on the CW shaft).

The mini guider is not really a match to this scope - I needed a finder and thought, what the heck, this way I can try it for guiding also but it is not long enough fl for the RC10, you could barlow it perhaps but you might introduce fexlure and have focusing issues.
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