SW 72ED stellar mira flattener and rotator back focus

[TiffsAndAstro]

hello again

 

has anyone tried using all three of the above together? is it possible to achieve decent back focus using this combination?

[PhilB61]

I found my SW72ed and flattener came to focus with the draw tube only about 5mm out, so concluded that if I added the rotator I would not be able to achieve focus.

[PhilB61]

The above comment assumes you are talking about the SW rotator that screws onto the focuser drawer tube. An alternative that might work would be a rotator fitted between the flattener and the camera, which could be used with suitable spacers to achieve the 55mm backspacing requirement.

[TiffsAndAstro]

just thought i'd mention this is my first telescope, so i might be a bit slow on the uptake of any advice

[Tomatobro]

Here is a photo of my setup. With the rotator, then the reducer, adapter, ZWO mini filter wheel and then the camera the EAF winds the focuser out to 9800 which is about 12 mm of focus tube showning.

Hope this helps

[Elp]

If you use a flattener which fits into the focuser like the 0.8x reducer I have you don't need a rotator, you just rotate the flattener and tighten back up.

Some screw on flatteners have built in rotators so please check.

Edited April 4 by Elp

[Elp]

If you're using your dslr you can't fit a rotator anyway as the Tring and camera take up the whole 55mm backfocus if that's the spec of the flattener.

[PhilB61]

Looking at Tomatobro's image above it seems my Stella Mira "adjustable flattener" puts the optical elements further away from the drawer tube than the dedicated SW flattener, hence why I had very little in travel remaining, don't know if that's the same with the non adjustable version or which one you have. As mentioned by Elp probably no need for a rotator if you are using the 2" push fit connector as you can lock it in any orientation

[TiffsAndAstro]

6 hours ago, Tomatobro said:

Here is a photo of my setup. With the rotator, then the reducer, adapter, ZWO mini filter wheel and then the camera the EAF winds the focuser out to 9800 which is about 12 mm of focus tube showning.

Hope this helps

it will help if you're suggesting i copy this but modified with the bits i don't have? could be a great help ty

[TiffsAndAstro]

6 hours ago, Elp said:

If you use a flattener which fits into the focuser like the 0.8x reducer I have you don't need a rotator, you just rotate the flattener and tighten back up.

Some screw on flatteners have built in rotators so please check.

its the one on flo website stellarmira. i'd hate to send the rotator back but if it rurns out i could do with out it that would be ace. im not sure how much i'd need or want to rotate.

https://www.firstlightoptics.com/adapters/sky-watcher-evoframe-camera-rotator-for-evostar-72ed-ds-pro.html

https://www.firstlightoptics.com/stellamira-telescopes/stellamira-2-inch-field-flattener-with-m42-adapter.html

Edited April 4 by TiffsAndAstro

[fozzybear]

can you post a photo of how you are currently setting this up?

[WolfieGlos]

46 minutes ago, TiffsAndAstro said:

its the one on flo website stellarmira. i'd hate to send the rotator back but if it rurns out i could do with out it that would be ace. im not sure how much i'd need or want to rotate.

https://www.firstlightoptics.com/adapters/sky-watcher-evoframe-camera-rotator-for-evostar-72ed-ds-pro.html

https://www.firstlightoptics.com/stellamira-telescopes/stellamira-2-inch-field-flattener-with-m42-adapter.html

Correct, you will need the rotator if you want to be able to rotate the camera.

However, I believe it depends which model of the 72ED you have. There was an older version with a shorter draw tube that, if I recall correctly, could not use the rotator since it didn't have enough travel distance to achieve focus. If you have the later version (which TomatoBro shows in his image) - which is the version I have - then it will be fine. You'll know it because it has that handy black label saying to connect the 360 degree rotator  

I have both the Stellamira flattener you have linked, and the skywatcher 0.8 reducer with a rotator for each. They are the Skywatcher rotator and one from RVO , and I'll be honest with you, they are both terrible. Whilst you can rotate the camera, it introduced horrible tilt into my system which I had already spent an age removing (and not wholly successfully either). Rotating the camera undid all that hard work, since the they essentially acted like a tilt plate, and in the end, whilst I had the rotators, I gave up using them. I never got my tilt issue fixed again. Others may have had more success with them, but I really did not.

I may have been unlucky with my versions, so if you've already got it, try it and give it a go 🙂

[Elp]

1 hour ago, TiffsAndAstro said:

its the one on flo website stellarmira. i'd hate to send the rotator back but if it rurns out i could do with out it that would be ace. im not sure how much i'd need or want to rotate.

https://www.firstlightoptics.com/adapters/sky-watcher-evoframe-camera-rotator-for-evostar-72ed-ds-pro.html

https://www.firstlightoptics.com/stellamira-telescopes/stellamira-2-inch-field-flattener-with-m42-adapter.html

The flattener is the same as the 0.8x reducer flattener I've got, you simply insert it into the focuser on the scope. Rotate it however you want. No additional rotator needed.

As mentioned these type can introduce tilt which is why most prefer a screw on type.

[fozzybear]

for a screw on type you will need to remove the nosepiece and other items as per the OVL version FF. the Genuine Skywatcher is a screw on type https://www.firstlightoptics.com/ed-pro/skywatcher-85x-reducerflattener-for-evostar-72ed-pro.html

 

[TiffsAndAstro]

2 hours ago, WolfieGlos said:

Correct, you will need the rotator if you want to be able to rotate the camera.

However, I believe it depends which model of the 72ED you have. There was an older version with a shorter draw tube that, if I recall correctly, could not use the rotator since it didn't have enough travel distance to achieve focus. If you have the later version (which TomatoBro shows in his image) - which is the version I have - then it will be fine. You'll know it because it has that handy black label saying to connect the 360 degree rotator  

I have both the Stellamira flattener you have linked, and the skywatcher 0.8 reducer with a rotator for each. They are the Skywatcher rotator and one from RVO , and I'll be honest with you, they are both terrible. Whilst you can rotate the camera, it introduced horrible tilt into my system which I had already spent an age removing (and not wholly successfully either). Rotating the camera undid all that hard work, since the they essentially acted like a tilt plate, and in the end, whilst I had the rotators, I gave up using them. I never got my tilt issue fixed again. Others may have had more success with them, but I really did not.

I may have been unlucky with my versions, so if you've already got it, try it and give it a go 🙂

No idea which version I'm getting. They seem popular so I assume I'm getting a later one.

I'll attempt assembling it all without the rotator and see if I can focus. If I feel the need to rotate, I'll try rotating the OTA in it's rings.

Would the rotator be suitable if I get a osc in future.

Ty all again for the help. About to Google "my first telescope help"

[TiffsAndAstro]

1 hour ago, fozzybear said:

for a screw on type you will need to remove the nosepiece and other items as per the OVL version FF. the Genuine Skywatcher is a screw on type https://www.firstlightoptics.com/ed-pro/skywatcher-85x-reducerflattener-for-evostar-72ed-pro.html

 

Apologies, might have to ask you more questions once it arrives and I've googled nosepiece

[Tomatobro]

Flo confirmed my scope was the first of the long tube versions sold by them.

Edited April 4 by Tomatobro

[TiffsAndAstro]

1 hour ago, Elp said:

The flattener is the same as the 0.8x reducer flattener I've got, you simply insert it into the focuser on the scope. Rotate it however you want. No additional rotator needed.

As mentioned these type can introduce tilt which is why most prefer a screw on type.

Yeah I've seen few videos that mention the tilt, also the camera hanging off a 5mm connector. But not entirely sure what they mean. 

When I try slapping it all together tomorrow (I've pre prepared my set of highly calibrated hammers) I will do it on a bed for safety;)

I might have more context after that 

[TiffsAndAstro]

2 hours ago, fozzybear said:

can you post a photo of how you are currently setting this up?

If you mean me, sure

Once it arrives and I've laid out my telescope adjustment hammers.

sadly, the vixen dovetail won't colour coordinate with my mount, so we may have to shield out eyes

oh yeah, and wires. Lots of wires. And if proper tripod hasn't arrived, imagine my £5 flea market tripod is an amazing one, robot hewn out of  carbotanium. And gold.

Edited April 4 by TiffsAndAstro

[TiffsAndAstro]

2 hours ago, Tomatobro said:

Flo confirmed my scope was the first of the long tube versions sold by them.

So mine must be the long tube version, too? Which means less of my image train will be hanging on a bit tighter so maybe less chance of tilt?

I won't be doing any rotating for a little while as I get used to this thing.

[AstroNebulee]

I have the older long tube version of the SW 72ed and had the ovl flattener which is basically the Stella mira one and use the RVO rotator which was excellent on my scope and so much better than the SW one. I had about 5mm of focus tube showing and able to achieve focus. 

Lee 

Edited April 5 by AstroNebulee

[TiffsAndAstro]

1 hour ago, AstroNebulee said:

I have the older long tube version of the SW 72ed and had the ovl flattener which is basically the Stella mora one and use the RVO rotator which was excellent on my scope and so much better than the SW one. I had about 5mm of focus tube showing and able to achieve focus. 

Lee 

Ty so much this, will attempt follow it with my stuff.

Bit apprehensive about it tbh 

[Tomatobro]

38 minutes ago, TiffsAndAstro said:

Bit apprehensive about it tbh 

I can understand this as it can be all a bit confusing.

I always do my setup tests in daylight. I aim the scope at the top of a distant tree, set the camera to a very short exposure and see what I get.  If the scope is a total unknown back focus wise I improvise something without all the reducers etc just to get an idea of what the measurement is. The cardboard tube from the inside of toilet rolls can be useful for this. It excludes the light and you can slide it in and out watching the monitor till a rough focus position is found then mark it with a pen. Now I can start putting together spacers etc.

[TiffsAndAstro]

I was just about to chuck a couple of toilet roll tubes in recycling

Stuff should arrive before twelve so soon see how I get on

[AstroNebulee]

5 hours ago, TiffsAndAstro said:

Ty so much this, will attempt follow it with my stuff.

Bit apprehensive about it tbh 

It can be but once you've cracked it you shouldn't have to do it Again. Unless you change something with the imaging train. 

Tomatobro gave good advice to try it during the day on a far away object. Even when it's partially cloudy at night give it a go too.

Good luck, you can do it 👍. 

Lee 

Edited April 5 by AstroNebulee