Contemplating a Celestron SCT C8, additional equipment needed, request for comment

[chris_g]

Hello all,

Looks like some Celestron C8-A XLTs are back in stock. I'm thinking about connecting one to my DSLR

Items needed
C8-A OTA
SCT T-Adapter
I already have both M42 and M48 T-Rings
Celestron f/6.3 Reducer Corrector

I want to add a filter to the image train, any recommendations on the best way to do that?

As far as guiding is concerned, I was thinking about using the ED80 with the ASI 290mm, weight wise everything would ride on the EQ6, really close to 50% rated weight and it would look really If I went with an OAG, the scope would ride on the AZ-EQ5 which would be my ultimate goal, any recommendations on what OAG.

And one final question, have I missed anything?

Edit:

Got some feedback from support for company I use, here's the updated equipment list

C8-A
WO SCT thread adapter for 2"
Blue Fireball Filter Drawer with M48/M42 Threads
F/.63 Reducer.
ZWO-L OAG

If I have the optical lengths correct for each device, I should need 8.1mm additional back focus and I have that on hand with a 7.5mm to 16mm variable.

That brings me to collimation, Celestron web site talks about a process done in the field. Since I started my journey with refractors, I know what the word means and what needs to be done but have never actually done it. A quick query indicates Bob's Knobs upgrade and a tri-Bahtinov mask. Okey dokey, collimation confirmed each time in the field when checking focus

Adding
Farpoint Tri-Bahtinov Focus and Collimation Mask for Celestron 8" Classic SCT
One set of Bob's Knobs for the C8

Ok, now, did I miss anyting?

As always thanks for looking, any and all comments welcome!

[JayTee]

Wow Chris, it sounds like you've got everything covered.

Some thoughts, SCT's don't go out of collimation very often. I check my C11 and it hasn't been out of collimation in 3 years. Also, if you use Bob's knobs, which I don't, always remember that if you screw one knob in then you have to unscrew the other two otherwise you can put undue pressure on your secondary.

Other than that it sounds like you're good to go. Good luck.

[Lady Fraktor]

Second JT comment on SC collimation, very rarely needs to be done unless you are bowling with it.

[Bigzmey]

I feel that Bob's knobs are not really necessary for SCTs. They should come well collimated from the factory (at least mine did) and if you don't mess with collimation (like replacing screws with Bob knobs ) it will last for years. If you ever need adjustment it will be just fraction of turn on one or two screws, super easy!

[chris_g]

Second JT comment on SC collimation, very rarely needs to be done unless you are bowling with it.

Haven't been bowling in a long time but I could probably roll about the same with a bowling ball as the SCT as I did then!

Thanks everyone for the confirmation and info on collimation of the SCT. Conferred with the wife, she gets her vacation to Florida for her birthday and I get a new telescope for my birthday coming up a little over a month from now. When I first started the journey I researched a lot of tubes, the Celestron XLT series were one of them, I had decided on a C9.25 as one of the tubes to eventually add to the kit after I got the ED80 but when the C8 became available when the timing was right with finances was fortuitous. I added the EAF bracket and will use the focuser motor from the ED80 and restore it with it's original focuser knob, I doubt it will be used for AP again by me, though I do have plans for visual in dual OTA mode with the it and the C8 on the AZ-EQ5

Just placed the order, now I wait, always the hardest part...

Celestron C8-A XLT 8" f/10 SCT Optical Tube with CGE Dovetail # 91024-XLT
Celestron f/6.3 Reducer Corrector Lens # 94175
ZWO EAF Bracket for Celestron C8 and C9.25 SCT Telescopes # ZW-EAF-C8-C925
William Optics SCT Thread Adapter for 2" Diagonal - Gold
Blue Fireball Filter Drawer with M48/M42 Threads and Extra Filter Holder - For 2" Mounted or 36mm Unmounted Filters # P-23
ZWO Large Off-Axis Guider for Full Frame Cameras with 1.25" Holder# OAG-L
Farpoint Tri-Bahtinov Focus and Collimation Mask for Celestron SCT/RASA Telescopes, Mask Size, 8in Classic

[notFritzArgelander]

Well, here's a recommendation for Bob's Knobs. Maksutov Cassegrains like my MK66 also rarely need collimation. I don't bowl with it but I do haul it around a lot in a car. Two cross country trips in its (so far 19 year) life and it has needed collimation twice. Once after one such and once after travel to a dark site on a virtually nonexistent road. I like the security of Bob's Knobs since I am a klutz and can easily see myself slipping with a screwdriver and scratching the corrector plate. The MK66 is Bob's Knobified.

[chris_g]

Well, here's a recommendation for Bob's Knobs. Maksutov Cassegrains like my MK66 also rarely need collimation. I don't bowl with it but I do haul it around a lot in a car. Two cross country trips in its (so far 19 year) life and it has needed collimation twice. Once after one such and once after travel to a dark site on a virtually nonexistent road. I like the security of Bob's Knobs since I am a klutz and can easily see myself slipping with a screwdriver and scratching the corrector plate. The MK66 is Bob's Knobified.

My hands don't work to well for fine detail any more, I'll order the knobs when I actually need to collimate it. I'd probably end up dropping one because I backed it out to far, I've drop screws every time I work in my lap top with those size screws and that would totally suck. No need to mess with the screws until I have to.

[chris_g]

One change to the order, changed the OAG-L to the OAG M48/M42. It has all the adapters needed other than extension tubes to connect a DSLR in this configuration. The tube will also not create an image circle large enough for a full frame sensor. Updated equipment list...

Celestron C8-A XLT 8" f/10 SCT Optical Tube with CGE Dovetail # 91024-XLT
Celestron f/6.3 Reducer Corrector Lens # 94175
ZWO EAF Bracket for Celestron C8 and C9.25 SCT Telescopes # ZW-EAF-C8-C925
William Optics SCT Thread Adapter for 2" Diagonal - Gold
Blue Fireball Filter Drawer with M48/M42 Threads and Extra Filter Holder - For 2" Mounted or 36mm Unmounted Filters # P-23
ZWO Off-Axis Guider with 1.25" Holder and M48 / M42 Threads
Farpoint Tri-Bahtinov Focus and Collimation Mask for Celestron SCT/RASA Telescopes, Mask Size, 8in Classic

[chris_g]

UPS confirmation, new tube should be here Thursday, checked the forecast and believe it or not, should be clear skies from Thursday through Monday of next week, getting about 6 hours of potential DSD time each night, wow! Now only if I can figure out how to get the new tube configured in time for this weekend, I will be giving it my best effort, really looking forward to some visual with it! Not a lot of targets for the wide field scopes yet, need to give it about another month or so or stay up really late as they start to get above my tree horizon around 01:30.