A thinnest high-quality manual or electronic rotator (CAA)

[Vroobel]

Hi.

I know that the CAA is not a camera, but it's closest to the discussion subject. Sorry, if someone asked the question earlier, but I didn't find the answer if any exists here.

My question is what is a thinnest manual (but high-quality one) or electronic rotator. I found one 16 or 16.5 mm thick, while others are only thicker. I'm a user of an Askar FMA230 which has a back focus 52-53mm instead of the declared 55mm and I'm not the only one. I like it and I don't want to swap it with another small scope, but using an ASI 2600MM-Pro cam and a 7 x 2" EFW with its 2mm thick M54/M48 reducer I'm limited now to 13mm only. 

I'm very curious if I missed something in the market. 

Thanks for your help in advance. 

[vlaiv]

I don't know if this qualifies as high quality one - but it is just 5.5mm thick:

https://www.teleskop-express.de/shop/product_info.php/info/p5547_TS-Optics-T2-Thread-360--Rotation-and-Quick-Changer---5-5mm-short.html

I have it on my wide field setup - Samyang 85mm T1.5 lens + suitable adapter and ASI178mcc

[Vroobel]

Thank you Vlaiv, it's indeed very thin. I'd like to use it with an APS-C camera and 20+2 mm EFW, isn't the M42 too small for 39.5 mm from the camera sensor? And isn't 1,350 kg a risky amount?

Thanks and CS

[vlaiv]

2 minutes ago, Vroobel said:

Thank you Vlaiv, it's indeed very thin. I'd like to use it with an APS-C camera and 20+2 mm EFW, isn't the M42 too small for 39.5 mm from the camera sensor? And isn't 1,350 kg a risky amount?

Thanks and CS

Maybe place it between camera and filter wheel?

That way you will only have weight of the camera hanging on it and that is probably a bit less.

M42 also won't be a problem as I'm guessing you are already using that to connect EFW with the camera?

Only drawback is that you'll need to redo flats when you change camera orientation (which you should really do anyway just in case telescope is causing uneven illumination and not just filter wheel / dust on filters).

You can always see if there will be any vignetting by using approximation. You say that you are at 40mm away from sensor and you are using M42 - so let's say that you have 38mm of clear aperture (2mm on each side for adapter). APS-C diagonal is ~28mm so we have (38 - 28) / 2 = 5mm of "room" on each side.

In order for light beam to converge 5mm in 40mm of distance - you need to be at F/4 or faster (that is 10mm of aperture over 40mm of distance or 5mm from center down to center). I think you'll be fine at that distance with most scopes unless you have very fast optics - faster than F/4.

[Vroobel]

Just now, vlaiv said:

Maybe place it between camera and filter wheel?

That way you will only have weight of the camera hanging on it and that is probably a bit less.

M42 also won't be a problem as I'm guessing you are already using that to connect EFW with the camera?

I cannot do it, the camera is screwed straight to the EFW, so it's the first part after the camera.

I can experiment and screw in an M48/M42 reduction behind the EFW to check the vignetting. I use an Askar FMA230 which is F/4.6.

 

[Vroobel]

I'd like to update this thread in case someone has a similar problem.  

Recently I bought two used M54/M54 manual rotators from @rsarwar. One of them has a male M54 / female M48 reduction ring which is great for me, I had only screwed it in deeper to obtain a proper length. It matches perfectly with the 7x2" ZWO EFW with its M54 thread while the second side can be screwed to the Askar thanks to the reducer.

I still think about the 5.5mm rotator, but I'll try to find a similar one with M48 or M54 thread. The extremely low profile would allow me to make an electronic rotator based on that. Thank you, Vlaiv.

CS,

[Clarkey]

I got one of these. 12.5mm thick. I thought it would be really poor, but it is actually very smooth and does not move at all. Holds my 1600mm and filter wheel no problem.

https://www.aliexpress.com/item/1005003279695931.html?UTABTest=aliabtest481469_657498&src=google&src=google&albch=shopping&acnt=494-037-6276&slnk=&plac=&mtctp=&albbt=Google_7_shopping&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=17859472720&albag=&trgt=&crea=en1005003279695931&netw=x&device=t&albpg=&albpd=en1005003279695931&gad_source=1&gclid=Cj0KCQiA2KitBhCIARIsAPPMEhLTLkAfDYp7Ma4wdJBuNQrt_M1k1jcWA7ZBuzXiKQhHQq-cRGfRaIkaAuogEALw_wcB&gclsrc=aw.ds&aff_fcid=a1fef4d7886f4bed90c532c4f34b6941-1705697101389-07968-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=a1fef4d7886f4bed90c532c4f34b6941-1705697101389-07968-UneMJZVf&terminal_id=4a377cf5f14743aba676a791ef9a56a1&OLP=1086700608_f_group3&o_s_id=1086700608&afSmartRedirect=y

[Adam J]

On 13/01/2024 at 23:02, Vroobel said:

I cannot do it, the camera is screwed straight to the EFW, so it's the first part after the camera.

I can experiment and screw in an M48/M42 reduction behind the EFW to check the vignetting. I use an Askar FMA230 which is F/4.6.

 

Why not just rotate the whole scope in its rings? Seems no disadvantage to doing that with the FMA230, it has no focuser to orientate for example and the guide scope wont be attached to the tube, its on the rings. 

Adam

Edited January 20 by Adam J

[Vroobel]

It's difficult to rotate the whole scope while a Deep Sky Dad's EAF adapter is used. Rotation by 90* means turning a focusing ring also by 90* in an opposite direction that causes significant change of the focus point. This affects a whole filters offset settings. The FMA230 isn't a typical refractor. 

[Vroobel]

On 19/01/2024 at 20:49, Clarkey said:

I got one of these. 12.5mm thick. I thought it would be really poor, but it is actually very smooth and does not move at all. Holds my 1600mm and filter wheel no problem.

https://www.aliexpress.com/item/1005003279695931.html?UTABTest=aliabtest481469_657498&src=google&src=google&albch=shopping&acnt=494-037-6276&slnk=&plac=&mtctp=&albbt=Google_7_shopping&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=17859472720&albag=&trgt=&crea=en1005003279695931&netw=x&device=t&albpg=&albpd=en1005003279695931&gad_source=1&gclid=Cj0KCQiA2KitBhCIARIsAPPMEhLTLkAfDYp7Ma4wdJBuNQrt_M1k1jcWA7ZBuzXiKQhHQq-cRGfRaIkaAuogEALw_wcB&gclsrc=aw.ds&aff_fcid=a1fef4d7886f4bed90c532c4f34b6941-1705697101389-07968-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=a1fef4d7886f4bed90c532c4f34b6941-1705697101389-07968-UneMJZVf&terminal_id=4a377cf5f14743aba676a791ef9a56a1&OLP=1086700608_f_group3&o_s_id=1086700608&afSmartRedirect=y

Yeah, it's exactly the same. 

I can see a tiny coma on one edge, depending on the camera position. My 7x2" ZWO EFW with filters and the camera weight more than 1kg, and they pull the camera side of the rotator down, but it's still acceptable. I'll wait a bit, it looks like ZWO plans to introduce their own rotator. 

Edited January 22 by Vroobel

[Adam J]

On 20/01/2024 at 12:41, Vroobel said:

It's difficult to rotate the whole scope while a Deep Sky Dad's EAF adapter is used. Rotation by 90* means turning a focusing ring also by 90* in an opposite direction that causes significant change of the focus point. This affects a whole filters offset settings. The FMA230 isn't a typical refractor. 

Yeah, that's why I made my own focuser adapter and mounted it to the tube itself so that everything rotates as one. You dont need all the complicated sliding stuff he uses as to focus all you need is 5 -10 degrees of total focuser turn, so the longitudinal movement during autofocus is nothing and can be taken up totally by a tiny bit of belt flex. DSD is a over complicated solution. 

Adam

 

 

Edited January 21 by Adam J

[Vroobel]

Thank you Adam, I'm going to consider this idea. 

Edited January 21 by Vroobel