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What Upgrade Astrograph to mount on a CPC925 Goto

AndrewG

By AndrewG
in Discussions - Scopes / Whole setups

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AndrewG

AndrewG

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Currently have a ST80 mounted on my CPC925 with wedge for autoguiding but would like to take some widefield shots using the CPC as the guider; any advice on what would be the ideal upgrade scope / astrograph for the widefield work given that I do not want to damage the CPC mount with excessive weight or do I just use the ST80?

At this stage any help would be most appreciated.

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ollypenrice

ollypenrice

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You might consider a Canon EF200L lens. Peter (Psychobilly) has demonstrated that on a Canon camera you can use it wide open at F2.8 if you focus on a star located at the intersection of the 1/3 lines. It's optically superb and gives a great wide field.

Otherwise something small and fast. A Mini Borg? A ZS66 or 72 with flattener? The ST80 will give extreme field curvature and grim blue bloat.

Olly

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Psychobilly

Psychobilly

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Here's a link to the thread about using the 200/2.8L at f2.8... all on an EQ3 Pro unguided etc... with an APS-C sized sensor rtaehr than a Full Frame one...

http://stargazerslou...-shapes-at-f28/

Unfortunately I like most of the others in the western side of the UK havent had a chance to get out much this "summer" to do some guided shots with thise camera lens combo onthe OBS mount (a CPC800 on a wedge)

Are your looking for something fast to properly illuminate the full frame sensor on your 5D?

Peter...

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AndrewG

AndrewG

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You might consider a Canon EF200L lens. Peter (Psychobilly) has demonstrated that on a Canon camera you can use it wide open at F2.8 if you focus on a star located at the intersection of the 1/3 lines. It's optically superb and gives a great wide field.

Otherwise something small and fast. A Mini Borg? A ZS66 or 72 with flattener? The ST80 will give extreme field curvature and grim blue bloat.

Olly

Thanks for the info Olly, given the following I think it would be better to go with a dedicated small / fast scope:-

1) The canon EOS 5D Mark II (full frame) is not compatible with an internal light polution filter (i have had to use a 2" Astronomic rear cell fitting version).

2) Eventually I want to upgrade to a dedicated CCD and use a filter wheel.

Andy

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AndrewG

AndrewG

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Here's a link to the thread about using the 200/2.8L at f2.8... all on an EQ3 Pro unguided etc... with an APS-C sized sensor rtaehr than a Full Frame one...

http://stargazerslou...-shapes-at-f28/

Unfortunately I like most of the others in the western side of the UK havent had a chance to get out much this "summer" to do some guided shots with thise camera lens combo onthe OBS mount (a CPC800 on a wedge)

Are your looking for something fast to properly illuminate the full frame sensor on your 5D?

Peter...

Peter thanks for the information; the photo's on the link looked great, as you had the APT sensor did you use an internal light polution filter? Unfortunately I was unable to get an internal filter for the full frame so have had to use the Astronomic 2" rear cell version.

I think I am going to go down a dedicated scope route given that eventually I would like to use a dedicated CCD with filters..

Andy

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ollypenrice

ollypenrice

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Agreed, the SCT with the frac on top will be very heavy, though, and the center of it's weight will be squarely placed at one point on the mount - would a T-saddle be better?

I used to use an inverted Baader Vixen dovetail fixed to the SCT and an inverted Baader mini-saddle attached to a ZS66 when I did this. It worked fine. You can see them here;

http://www.baader-planetarium.de/sektion/s03/s03.htm

Olly

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AndrewG

AndrewG

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This is for piggybacking on an SCT fork so it needs to be small. Borg astrograph? Small WO with flattener?

Olly

Thanks for all the information, looking on the net would the Borg 71FL Series 80 be a good choice given its so light (1.2 kg) or would you propose something better.

With regards mounts I already have the ADM dovetail bars fitted and currently use rings; looking at your other posts would you use something more ridgid rather than the rings to prevent flex.

Andy

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AndrewG

AndrewG

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I wouldn't use rings. The scopes are too short so I'd use one of those Baader clamps in the link above. The Borgs have a good name if you can unravel how to build one up!!

Olly

Thanks Olly..

What do you mean by build it up, are they not assembled? As I am now in this for the long game what would you buy if not the Borg given I want to photograph the larger nebulas (& Andromeda) which are too large for the CPC @ f6.3?

Thanks for all the help as I do not want to spend any more money wishing I had done something different I.e. It all started out a few years ago... with just visual / planetary in mind hence the CPC was a good choice then the imaging bug started, which resulted in a wedge, then guiding and as the whole thing was just too heavy to lug around the observatory got delivered!!! The final piece was the wife having to have a conservatory cause I had an observatory :grin: ... ahh.

Andy

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ollypenrice

ollypenrice

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The Borgs are modular and come in a variety of configurations. You just need a dealer to talk you through it!

If you want the best small refractor for imaging it would be dead easy to point to the Takahashi FSQ85ED which, to the best of my knowledge, has no serious rivals. But small it ain't and cheap it ain't...

Olly

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AndrewG

AndrewG

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Money aside I think I will try the Borg route given I do not want to put too much weight on the cpc mount; when I manage to get it and have a clear night I will post any results.

Many thanks for all your help again Olly. P.S looks gud in the south of France; maybe one day (subject to talking the misus into a stay) I could get to try out your Takahashi!!! :laugh:

Andy

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