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Originally Posted by astronobob
Great stuff Marc 
Quite a straight forward & compact Focal train you have there Marc, which looks Ideal (Appreciate the pics there aswell  ) |
Yeah everything is bolted. Makes it rigid and square. Focus is via the primary, which is the best way to do it.
Quote:
Originally Posted by astronobob
I have some parts & kit around, a meade OAG & an Orion thin OAG which I'd prefer but may not suit/adapt to the meade threads, may be some adapters, tho Id like to avoid them as 'simple is key ?
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Either OAG will be alright. Adapters are ok too as long as they don't narrow the light path. Try to keep the inner diameter of your rig as close as the inner diameter of your exiting baffle tube, right up to the camera sensor. An added benefit is that you can have more light getting in the pick up prism from your OAG. Most adapters to the back cell restrict the diameter to 1"1/4 already. If it's the case bin it and make your own.
Quote:
Originally Posted by astronobob
Either way with most likely qhy5, its nice and tiny to sneak in cramped places & quite sensitive for a guide star
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The QHY5 will be nice for guiding with a pick up prism. Not sensitive enough for an AO but sufficient for standard guiding. Also it is quite big in diameter so sometime you won't be able to get it down close enough to the main light path and you might need spacers, then the same spacers before your imaging camera to match focus.
Quote:
Originally Posted by astronobob
- so they call it 'Fishing' I can understand this as have used the Orion OAG on the 10" Newt F4.7 tho ? Think my targets with the 12" will be determined by How many stars are in the small field  Quite a few good galaxies out there in the middle of nowhere 
My scope is a Meade 12" ACF which Id like to use with the Qhy10 C and Im hoping to fit the Moonlight motor focuser in there somewhere - then I can Lock the mirror down - It'll all be Trial & Error for a while, I'm sure of that  And no doubt all easier said than done  |
Try not to do that. The 12" is a large heavy chunk of glass and will move regardless. Stick with the original design. Bolt everything at the back and focus with the primary. Keep it simple. Save a couple of bobs. No pun intended.
Adding a focuser at the back will introduce an extra point of flexure and weight to the rig. Image close to the zenith. Your primary will always move whether you like it or not. Locking it won't work and will introduce aberrations with temperature gradients. It needs room to breathe.
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Originally Posted by astronobob
Im currently in the process of sorting out some ventilation fan/s for the scope cover 'Cosmo Caboose', pretty hot in there otherwise, then Ill start rigging up and piecing things together...
Cheers for all your time, feedback, answers , pics and advice Marc |
I did add some fans at the back of my C11 primary cell. I use them only when the air is dry and when it's very hot. Other than that it's best to keep the air inside the scope as "clean" as possible. Don't push in moist air or you'll dew the inside of the corrector and possibly the primary. In QLD I assume you have high humidity. If the inside of your scope is hot and dry then it's better than cooler and moist. It will equalise eventually. May be a very tiny PC fan inside the scope tube aimed at the baffle tube to disrupt the boundary layer on your primary would work better.