Guide cam and setup advise for C8.

[HighHo]

My bonus time at work is coming up and looking to get a guide cam to my setup, currently I have a Celestron AVX with C8 SCT VX and using a DSLR Nikon 5300 . I do already have an OAG I picked up from e-bay ( seems to be this: http://www.firstlightoptics.com/off-axis-guiders-oag/off-axis-guider.htmlbut with addtioanl extention tubes supplied). Even with the OAG avialble im not against using a guidescope depending on peoples experince. I would say my budget is £500 - £1000 although I would like it the lower end of this (or cheaper!), it should cover all the addtioal equipment needed (ie if recommeding with guidescope it should include the fixxings needed). I generally get out when I canwith my scope  which is a mixture of light poluted skies from my garden, and some nice dark skies when getting out is possible.

I know theres maybe no simple answer, so just looking for peoples experinces. Thanks in advanced for any help.

[Thalestris24]

Hi

I think the general concensus is to use an oag with an sct on account of the imaging scope's long focal length. I don't have an sct myself but, fwiw, I use qhy5l-ii mono cams as guide cameras - about £220, I think. Might be cheaper from the continent as £ is strong against the Euro. They are sold as ALCCD... over there, e.g. http://www.teleskop-express.de/shop/product_info.php/language/en/info/p5635_ALccd-QHY-5-II-CMOS-Guider-and-Planetary-Camera-with-monochrome-sensor.html

Hth

Louise

[Geordie mc]

I agree that an oag would be better that a guidescope. The Starlight Express lodestar and the lodestar x2 are very good, especially the latter which is much more sensitive allowing the use of less luminous guide stars. Think it's about £430. Having more sensitivity also helps with oag systems as the prism only picks off a small amount of light.

[Benno]

Hi, I also have the Celestron C8 SCT on the AVX mount and I went through the dilemma of what auto guiding system would be best to use.

I know the general consensus for guiding with an SCT is to use OAG in order to get round the issue of mirror flop etc. However when I started looking into my guiding set up I read numerous articles and spoke to a few people at the local astronomy club and came across quite a few comments regarding 'tricky' set up and restriction with regards to finding a suitable guide star in the resulting field of view  ( I must say that I have not tried an OAG set up therefore can not comment on these points).

I then started to consider using a guide scope and once again after asking lots of questions and doing more on line research and taking into account the issues associated with guide scope  auto guiding such as 'flex' etc. I opted to go with the 'Orion mini guide scope' and 'Orion star shoot autoguider'.

The points to note with this set up are:-

The guide scope is suitable for guiding scopes of up to 1500mm focal length, the C8 has a focal length of 2032mm, I found the Celestron F/6.3 focal reducer reduces the apparent focal length to 1280mm which is well inside the capabilities of the Orion guide scope.

I also found that the standard dovetail foot mount supplied with the Orion mini guide scope was not suitable for mounting on the SCT so I purchased an additional foot designed for the SCT (cost about £14.00), which mounted perfectly.

I am not saying that this is the best set up to use but it is an option if you are thinking of moving away from OAG. I have found that it works really well for me.

The added bonus is that the total cost for the whole set up would be just under the £500 budget.

Best regards,

Benno.

[HighHo]

Thank you all for the feedback, I will go for the OAG option and  to start with but keep enough aside for a guide scope if needed. I do worry about back focus with the OAG and/or finding a guide star, great to hear you have had a good experince Benno with a guidescope as our setups and camers are similar.

[ollypenrice]

I've used an OAG on a catadioptric. It's not just the relative focal length which matters but the fact that the primary mirror can move. An OAG will 'see' this movement and correct for it but a guidescope won't. You'll also save weight. The Lodestar Two should be a great guide camera. The original Lodestar is also a great camera ruined by an idiotically small ST4 cable. I have two of these in operation and both fall over from time to time as the poor ST4 connection does what it does best, which is fail to connect. You can pulse guide and lose the ST4 cable but I don't want to. I have a guide software which I understand inside out and I don't want to learn a new one.

Olly