Camera adpter

[muletopia]

Hello folks,
Using my Mewlon 210 for photography an Orion thin off axis guider is used. I just put the 2 inch nose piece in the visual back and away I go. Recently a QHY8l has replaced a Canon 60Da.
In either case the stars off axis leave very much to be desired. So I have just bought from Clade a corrector/flatener for the scope.
Problem, the output side of the corrector has a female thread .about 50 mm in diameter. Takahashi only sell a wide tmount adapter for this thread to Canon and Nikon cameras.


Somebody here must have mounted an OAG to camera arrangement to this correcter

I would surely like to know how.


Chris

[Dennis]

Hi Chris

I find that my Mewlon 210 is quite sensitive to having the correct Back Focus with my Tak x0.8 Reducer / Flattener (from 8-10 years ago). My R/F has a 2" Push Fit into the telescope end and a 54mm Female Thread at the camera end.

Not sure if the current model Tak x0.8 R/F has been updated in the meantime though?:shrug:

Also, I think it is a Reducer / Flattener rather than a Corrector, as I end up with slightly comatic stars at the edge of the field.

Here is my set up as an example.:)

Cheers

Dennis

[muletopia]

Thanks Dennis.
Your third picture looks something like I need.
The extension piece would have to be double with locking screws to allow the OAG to be rotated to find a guide star,

So how do you guide?
If with a guide scope what effects of primary mirror movement to you get?


Chris

[Dennis]

Hi Chris

I use a 560mm focal length Guidescope/SBIG STi Camera and have not experienced any problems with Primary Mirror movement, although I am only an occasional "set up every night" imager who runs sequences of between 60 mins to 120 mins.

Cheers

Dennis

[muletopia]

Again thanks Dennis,
I think a conversation with Joshua Bunn is in order. If Josh says "too hard" then an external guide scope it will have to be.
Cheers
Chris

[Dennis]

Have a look at the Australian QHY Dealer, his website lists several adapters.

http://www.gamaelectronics.com.au/accessories.html

I think the Tak x0.8 R/F is a Female 54mm thread and there are several 54mm M thread Adapters listed.

Cheers

Dennis

[muletopia]

Spot on Dennis,
Ringing Gama was on my to do list for today,but some how it did not happen, so thank you. One of the 54 mm adapters seems like part of the solution.


I have just sent multiweb a pm as he has used a QHY8L on a Mewlon 210,I hope he can also shed some light on the subject .


Chris

[muletopia]

Well it seems that mounting an off axis guider to an adapter is too hard at this stage.
So Joshua Bunn will make me a 54 to 42 adapter to hold the QHY sensor at the same distance from the flattener as the Tak supplied EOS Tring to EOS sensor plane.

The longest FL 'scope I think is appropriate as a guide scope has a FL of 700 mm.


So poorer guiding than off axis guiding for several reasons.


I wold like suggestions for a suitable guide 'scope,
Dennis, what do you use?


Chris

[Dennis]

Hi Chris

I use the only other 'scope I have, a William Optics 80mm F7 refractor with a fl of 560mm and find that it does a good job.

Its a bit of an overkill as it is an ED Apo but as I had it and the (fixed) rings, I just bolted it to the Tak Accessory Plate and it seems solid enough, if a little heavy.

I once had some 3-Point adjustable rings but never found them satisfactory, they seemed rigid enough but I got star trailing so I use the fixed rings now.

Cheers

Dennis

[muletopia]

Thanks Dennis, I am thinking of a Saxon 700/70 as a guide scope. The cheapest long fl scope I can find, I take on board your comments about. 3 point rings.I am not clear on how your finder is mounted, would you post a picture please.


Chris

[Dennis]

Hi Chris

An example of the WO Mounting Rings are shown here:

https://williamoptics.com/products/accessories/mounting/mounting-rings/mounting-rings-90mm

They clamp around the OTA and hold it firmly, but this means that the OTA is non adjustable, although I have always been able to find a suitable guide star for a 10 sec exposure with my SBIG STi Guider Camera.

Cheers

Dennis

[muletopia]

Thanks dennis,
Bintel sell 90 mm fixed rings which would fit the Saxon,step 1 So how is this lot attached to the Mewlon (or beside it)?

Chris

[Dennis]

Hi Chris

I use the Tak Medium Accessory Plate (on my EM200 Mount) that I purchased from an IIS member a while ago.

Here is a link to a photo that shows it.

https://telescopes.net/store/tmp0220-medium-m-accessory-mounting-plate-for-em-200.html

I drilled and tapped some M8 holes on the angled flange and bolted the rings to this on a small aluminium plate.

This gives you a fixed guidescope configuration, so you cannot adjust the guider scope if you cannot find a suitable guide star.

Cheers

Dennis

[Dennis]

As a follow up, in my own experience, fitting, balancing, and using a separate Guide scope (GS) has been quite a challenging experience leading to frustration and plenty of tears when things do not work.:(:sadeyes::mad2:

I used to have a dovetail saddle on the mount, then a side-by-side mounting plate with a saddle for my OTA and a saddle for the GS. This set was a bit heavy and cumbersome, but it did up allow me to move the set up side to side (laterally) and slide the OTA and GS in their saddles longitudinally to find the correct balance. I used to change cameras and accessories (Barlows, reducers, etc.) and this affected the set up, so I had to re-balance each time.

The Tak Plate came up on IIS from a member who I had trust in, in terms of looking after their gear and integrity so I purchased it “just in case” and put it aside for a year or so.:)

I then settled on a camera and system that was reasonably stable and began experimenting and noticed that the Tak Plate would more or less accept my OTA and GS in fixed locations (after drilling a few holes) and the system would be in balance based on my past experience with my gear. This is an important point, as I had gained an awful lot of experience (and frustration) with my gear by having the flexibility to make both lateral and longitudinal adjustments of the mounting plate, OTA and GS in my non-fixed side by side set up. I cannot over emphasise the flexibility that this side-by-side system offered, despite its weight.

The Tak Plate has given me a much more fixed side by side set up. If this had ended up being grossly out of balance, then there would be very limited options to move anything around and I would have had to resort to adding small weights at strategic locations to get balance, which is something I would have wanted to avoid.

So to cut a long story short, my previous experience and tinkering with an GS on a traditional and flexible side-by-side system gave me the confidence that the (fixed) Tak Plate would get me in the right spot in terms of balancing the OTA and GS and that was indeed the case.:)

I would probably not have started off with such a fixed system from Day 1, as it provides very little room to manoeuvre if your rig does not balance and from hard won experience, balance is critical to obtaining good guiding.

Cheers

Dennis

[muletopia]

For your patience many thanks Dennis,
I think I can stop bugging you now.
My gear rides on a Mesu 200 so I will arrange tube rings or v blocks on the Mewlon. Not a versatile as your setup where the guide scope is attached to the mount and not the scope.


Cheers
Chris

[Dennis]

Good luck Chris, I'm sure you'll work it all out.:)

Cheers

Dennis

[Dennis]

Just be careful with tube rings Chris, as if they are too thick then they will not easily fit under the fixed Tak Finder.:(

I managed to score a custom designed set of tubes for my M210 from another Tak M210 afficionado on IIS, so I was quite lucky.:)

I found the (thick and heavy) Parallax Rings for my old Mewlon 180 were a very tight fit under the M180 Finder and would not allow me to rotate the M180 OTA without the flat sections of the Rings fouling the Finder.

Cheers

Dennis

[muletopia]

Dennis,
I use the OAG as follows
slew to target, rotate the OAG (and imaging camera) until a suitable guide star is found then rotate the imaging camera in its rotating/centering ring to capture the target in the desired orientation.

This has always worked for me, just turn the guiding camera gain down so that PHD2
follows the centre of the coma distorted guide star.
Chris

[Dennis]

Hi Chris

I stuffed up my previous post and mistakenly wrote OAG when I meant separate Guide Scope so I have edited the post.:)

Cheers

Dennis