14 replies to this topic

[steven_usa]

I'm trying to adapt ZWO ASI1600MC-C to a Celestron 8SE SLT.

 

I was able to use a 2" diagonal but I'd rather just go straight back (and also inline a filter wheel eventually).

 

The Celestron 8SE scope has a threaded back.   Ideally I'd thread straight to the ZWO ASI1600, but also just getting a 2in "eyepiece" type adapter straight back might be good enough (and maybe make it easier to rotate/orient the camera).

 

There was a shop in Florida that used to make such adapters (I mean you'd select the components and they "made to order" the adapter, but you may have to experiment on the depth), not sure if they are still around.

[Oort Cloud]

You need at a minimum, a Celestron t-adapter, or some other SCT-f to M42-m adapter.

You should also get a correcting reducer as well. Celestron makes them, & Starizona makes better ones, but they're much more expensive.

Without a reducer, you can just attach the camera to the T-adapter and focus. With a reducer, you'll have to use a specific "working distance" from the end of the reducer to the camera sensor (usually 105mm), but it will greatly improve the coma and field curvature inherent to the SCT design, while also reducing f/# and focal length, which are both important for making an SCT practical for imaging things other than planets (those should always be done at f/10 or even higher).

Good luck.

Also, if you're using the alt-az mount that the SE scopes come with, forget everything I wrote above. You need to use a diagonal with alt-az or the scope won't be able to point straight up without hitting the mount. If that's what you're using, you need to switch to an EQ mount as soon as possible to any serious imaging. Alt-az is limited to about 15-20s usually due to field rotation.

[steven_usa]

Forgot I already had a Celestron f/6.3 reducer.

 

And I see preciseparts.com is still operational.

 

Recently I ended up with some red, green, blue "wiggle" lines after stacking some practice images, and that reminded me that dithering is important. 

 

I think I can use my existing ZWO EFW (filter wheel) that has an integrated OAG with it... I was looking at Celestron's OAG, and geesh, for that price maybe I should just consider going straight to HyperStar?  But I think in the past I had decided to wait on HyperStar till I was ready to move up to a 9.25 or larger scope.

 

So I'm thinking something like this...  

 

 

For the custom PreciseParts part, maybe it needs to be 50mm instead of 30mm?  I forget exactly how far back the ZWO ASI sensor is, probably 3-5mm.

 

What is Celestron's "native" back thread called? (the part highlighted in blue above)  Or is that "standard 2 inch T-2"?

 

 

And yep, you're right I do have the NexStar SE Alt//Az mount, but don't plan on using it or messing with a wedge.  I'll use the CGEM instead.  I might use the NexStar SE mount if I ever want to try planetary again.   The portability of that little NexStar SE is nice, but indeed the space behind the scope ends up very limited.

 

[steven_usa]

Does anyone know what "bolted" vs "M54" means for the PreciseParts listing of the ZWO EFW 5x2 wheel?

 

I asked PreciseParts, who said to ask ZWO.  I asked ZWO, they said to ask where I ordered from.  I asked High Point Scientific, and haven't heard back yet.

 

I could just try one and return if it ends up not working, but was hoping to avoid extra delivery back-and-forth for that. 

 

 

 

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[steven_usa]

Here is what the EFW I have looks like.   It does have some bolts (screws), but the thread is closer to "regular" 49mm than M54 ??

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Edited by steven_usa, 18 April 2024 - 02:27 AM.

[ayadai]

Get the SCT to 2” Adapter and use the 2" nosepiece for the camera. This is  a very flexible and inexpensive option (I also have a .63 reducer, filter wheel and tilt adapter installed):

 

 

 

Edited by ayadai, 18 April 2024 - 06:02 AM.

[Oort Cloud]

Here is what the EFW I have looks like. It does have some bolts (screws), but the thread is closer to "regular" 49mm than M54 ??

That is an M48 connection. Your setup for proper working distance is:

SCT (SCT M threads) --> SCT reducer (SCT F-SCT M) this is where you star measuring, and you need 105mm --> Celestron t-adapter (50mm long, SCT F-M42 M) --> on the M42 male threads, you spin on a ring that has M42 F on the inside, and M48 M on the outside (0mm Long), that will give you the threads needed to attach your image train, which is already 55mm long, thus beinging you to the total of 105mm. The ring with M42 inside and M48 outside, comes with the OAG.

Edited by Oort Cloud, 18 April 2024 - 02:05 PM.

[Oort Cloud]

Get the SCT to 2” Adapter and use the 2" nosepiece for the camera. This is a very flexible and inexpensive option (I also have a .63 reducer, filter wheel and tilt adapter installed):



IMG_20240418_183332_1.jpg

That EFW is far from the sensor. Even though the 183 is fairly small, I'm curious if you had to use filters larger than 1.25" to avoid vignette with that setup?

[ayadai]

That EFW is far from the sensor. Even though the 183 is fairly small, I'm curious if you had to use filters larger than 1.25" to avoid vignette with that setup?

I use 2" filters; there is no vignetting.

[steven_usa]

Get the SCT to 2” Adapter and use the 2" nosepiece for the camera. This is  a very flexible and inexpensive option (I also have a .63 reducer, filter wheel and tilt adapter installed):

 

 

Thanks - that was one thing I was looking for, just a 2" straight back adapter.  Just I couldn't remember if "SCT" was the term used for that standard 8SE back.   

 

When you get a chance, I'd love any info about a motorized auto focuser for this same 8SE (XLT if it matters, not an EdgeHD).  Come winter time, it's more fun to sip hot tea from inside and fiddle with focus remotely

 

I try to use all threaded connections (avoid thumb screws), but true I will need a tilt/rotator eventually.  I'll get that SCT to 2" just since I should have it in the kit.  But I'm also just going to try the PreciseParts and see how it works out - I've gotten good adapters from them in the past.  If you e-mail them, they'll insert a threaded filter support in just about any adapter you request.  For this one I'll just request they make it M48 instead of M54, and see if they'll accommodate that.

[ayadai]

When you get a chance, I'd love any info about a motorized auto focuser for this same 8SE (XLT if it matters, not an EdgeHD).  Come winter time, it's more fun to sip hot tea from inside and fiddle with focus remotely

I've the same scope. In terms of focus there are three avenues available:

1. Install a Celestron Focus Motor; the option I chose;
2. Install a 2-speed EAF-compatible focuser on the back and use it for fine adjustments;
3. Disassemble the scope, lock the mirror in place and install a 2-speed EAF-compatible focuser on the back.

The Celestron Focus Motor driver goes past the focus point then back by design to eliminate backlash and better secure the position of the mirror, minimizing image shift. Also, the Celestron driver is ASCOM compatible, allowing it to be easily controlled from within N.I.N.A.. After connecting the focuser in the ASCOM device hub, select "Drive Hub Focuser" in N.I.N.A..

 

I don't see enough advantage to the second option to justify the cost, and while the third option definitively eliminates image shift, the C8-SE is not significantly affected by the issue, so it's not worth the trouble and cost, IMHO. As always, YMMV.

Edited by ayadai, 18 April 2024 - 07:00 PM.

[Oort Cloud]

I've the same scope. In terms of focus there are three avenues available:

• Install a Celestron Focus Motor; the option I chose;
• Install a 2-speed EAF-compatible focuser on the back and use it for fine adjustments;
• Disassemble the scope, lock the mirror in place and install a 2-speed EAF-compatible focuser on the back.

The Celestron Focus Motor driver goes past the focus point then back by design to eliminate backlash and better secure the position of the mirror, minimizing image shift. Also, the Celestron driver is ASCOM compatible, allowing it to be easily controlled from within N.I.N.A.. After connecting the focuser in the ASCOM device hub, select "Drive Hub Focuser" in N.I.N.A..

I don't see enough advantage to the second option to justify the cost, and while the third option definitively eliminates image shift, the C8-SE is not significantly affected by the issue, so it's not worth the trouble and cost, IMHO. As always, YMMV.

I have both a 6se and a C8 EdgeHD. The edge has almost no flop, due to the way it rides the baffle tube, but my 6se definitely has some and requires an OAG to guide. I use OAG on the 8 as well, but that's because I already have it and it's bulletproof.

The overcorrection can be done using backlash adjustments on pretty much any focus motor and control software. Just measure the backlash in a live view and then set it and forget it. Just also make sure the motor direction is set so that AF runs finish in the CCW direction and that will ensure the mirror finishes by moving upward, toward the sky.

[ayadai]

The overcorrection can be done using backlash adjustments on pretty much any focus motor and control software. Just measure the backlash in a live view and then set it and forget it. Just also make sure the motor direction is set so that AF runs finish in the CCW direction and that will ensure the mirror finishes by moving upward, toward the sky.

Correct; ~$200 total cost plus ease of installation makes the Celestron focus motor a good choice.

[steven_usa]

Thanks for note about the Celestron Focus Motor, looks simple enough.  On the Vixen scope I had used a Starlight Instruments FeatherTouch, and got very spoiled having an electronic focuser.   I haven't tried NINA, I still have Sequence Generator Pro (SGP) though.   As the night cools, the auto-focuser was useful in maintaining the focus as the scoped warped across temperature changes.   Good for the deep long stares collecting hours of data, but not so critical for planetary obviously.

 

SGP and the auto-focuser also handled the meridian flip, combined with having your own star chart repo to do standalone plate solving to auto-recenter.  My Vixen got damaged a few years back in an unusual snow storm.  I picked up the 8SE to give it a try - I liked the open air Vixen, I'll see how dewing issues pan out on this Celestron closed can.

[Oort Cloud]

Thanks for note about the Celestron Focus Motor, looks simple enough. On the Vixen scope I had used a Starlight Instruments FeatherTouch, and got very spoiled having an electronic focuser. I haven't tried NINA, I still have Sequence Generator Pro (SGP) though. As the night cools, the auto-focuser was useful in maintaining the focus as the scoped warped across temperature changes. Good for the deep long stares collecting hours of data, but not so critical for planetary obviously.

SGP and the auto-focuser also handled the meridian flip, combined with having your own star chart repo to do standalone plate solving to auto-recenter. My Vixen got damaged a few years back in an unusual snow storm. I picked up the 8SE to give it a try - I liked the open air Vixen, I'll see how dewing issues pan out on this Celestron closed can.

Plan for dew.

SCTs are dew magnets, so much so that some of us refer to the corrector plate as the "collector plate" because collecting dew seems to be it's only purpose.

Unless you live somewhere dry, you'll probably need a dew shield at a minimum.