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Is my Field Flattener simply tilted, or something else wrong?


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Hi :)

So my issue is that every sub has stars at one corner pointing to the middle of the image, as if it's not being corrected by my Field Flattener.

This has been a problen since it was new, however when I got the FF I was using my astromodded Canon EOS 550d. As I astromodded it myself, I could not be sure that the tilt was not because of the sensor could have been tilted after the mod.

After that I have got a new camera, the ZWO asi 1600mm-c, and the tilt is still there. 

So the tilt is not in the sensor of the modded 550d, but is it the scope or the FF?

I have one even older sub with the scope + canon 550d and no FF. In this image it looks like all the stars are equally pointing from the edges towards the middle (no tilt).

 

So the FF in question is a SkyWatcher unit. It has one 'tube' that goes into the focuser, and one larger tube with the glass elements. Where the two tubes meet there is a self centering function. The smaller diameter tube 'fades' into the larger diameter tube with a radius that trails the circumference of the two tubes.

This does center the FF into the focuser tube, but that is where the issue lies I think? If the FF is sentered, then the smaller diameter tube on the FF is not making contact with the inside of the focuser tube, as the diameter is slightly smaller than the focuser tube.

When I then hang my filterwheel and camera on the FF, then it moves untill the FF tube and the inside of the focuser tube meets, making the optics tilted.

 

So if this is likely the case, then I can do one of two things.

1. cheep fix. Wrap the smaller tube of the FF with one or two layers of tape, so that the FF mets the inside of the focuser tube centered, and not making the optics tilt. 

2. get a new FF 

 

I really want to make my corner stars perfect. When I process something with the meridian flip, I get these stars in two corners, and they are not allways easy to process out.

I do need someone to agree with my findings, or point out something I missed before continuing. 

 

Here are the subs I'm trying to decode.

All the subs is with the SW Equinox 80 PRO APO

1. eos 550d, modded, no FF, no tilt, all corners pointing to the middle

2111899361_TULIP-2_LIGHT_200s_200iso_24c_550DT2i_20150725-01h08m30s859ms.thumb.png.e919d37c6abf49254062d18b4247f57a.png

 

2. Pelican

eos 550 modded, FF, Tilt, topleft and toprignt pointing towards center

1877858236_PELICAN_2_LIGHT_600s_800iso_26c_550DT2i_20150814-01h09m09s363ms.thumb.png.b3d0e30a98a9b5186ab4ad73eeacec45.png

 

3. California

asi 1600mm-c with FilterWheel, FF, Tilt, topleft pointing center

California_Light_Ha_300_secs_2017-01-15T23-04-08_010.thumb.png.2b095e3e192cb779480f58c8481a9a5c.png

 

4. New Pelican

asi 1600mm-c with FW, FF, tilt, topleft pointing center

ic5070__Light_Ha_300_secs_2020-11-22T19-08-39_005.thumb.png.41dcdce98a569cc8ec176bb3fd37935f.png

 

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4 minutes ago, Owmuchonomy said:

Looking at your subs, the whole frame is suffering with oval stars to a point so I guess the tracking/guiding is not optimum.  Regarding the corners is it worse on the chip that is the largest?

Guiding migt be more 95% than 100% on, but I think there is a lot worse in the corners. If you look at the stars in the middle of the last image (new pelican), they are a lot better than in the topleft corner.

The first pelican in colors is from the canon eos 550d. Ith has a APC-C sensor that is bigger than the asi 1600mm-c, and it has worse stars than the asi subs.

It looks like on the color pelican there is a issue on both top corners.

 

If it is a issue with the centering function of the FF then there will be differences. (I have unmounted and mounted everyhing several times for swapping camea, cleaning, etc, so the tilt would vary)

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Figured I could make a drawing of what I tried to explain in the first post.

Just a crossection of the FF in blue, with the self centering radius, and what I think is creating the tilt.

The box outside the blue is just the focustube.

How it ideally should work

focusFFcenter.thumb.png.5667c26cf74d42435bd6840850b12355.png

 

How it ends up with a filterwheel, camera and more hanging off it.

focusFFcenterTILT.thumb.png.97e5539b35091a3a060933b8aeadd987.png

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Yes, you have tilt of FF and ideally you want to have threaded connection in order to avoid this.

As far as I understand, SkyWatcher dedicated FF/FRs should have straight forward threaded adaptation to SW scopes?

Here is screen shot from FLO website:

image.png.38351ce6523bc1a30a10f05292b7252a.png

https://www.firstlightoptics.com/reducersflatteners/skywatcher-85x-reducer-flattener-for-ed80.html

 

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8 minutes ago, vlaiv said:

Comments on that one you linked say that it can use both 2" and M48 connection.

Does 2" nose piece unscrew from flattener? Does your focuser have any sort of threaded connection?

 

I think the aswer is no on both parts, but now I really want to figure out how to make that a Yes :)

I would have to check, to be sure, but a google search shows no threads. I wonder if there is a chanse to get a focus tube with treads, or some other upgrades to this scope.

I have had it since 2015, so I can afford some upgrades on it now.

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5 minutes ago, Magnus_e said:

I think the aswer is no on both parts, but now I really want to figure out how to make that a Yes :)

I would have to check, to be sure, but a google search shows no threads. I wonder if there is a chanse to get a focus tube with treads, or some other upgrades to this scope.

I have had it since 2015, so I can afford some upgrades on it now.

I'm just looking at focusers, and I think that best choice for you would be Baader Diamond Steeltrack refractor focuser.

You only have to make sure you have proper connection to your telescope to replace your stock focuser.  It will probably be either for flange ID 86 or ID 96 (that are two standard tube inner diameters for Skywatcher).

If it's ID 96 - then it is easy - you have ready made adapter:

https://www.firstlightoptics.com/baader-diamond-steeltrack-focusers/baader-steeltrack-diamond-rt-adapter-for-synta-sky-watcher-celestron-otas-with-id-97mm.html

And in the end, you only need M48 adapter:

https://www.firstlightoptics.com/baader-diamond-steeltrack-focusers/baader-diamond-steeltrack-m48-adapter.html

 

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6 minutes ago, vlaiv said:

I'm just looking at focusers, and I think that best choice for you would be Baader Diamond Steeltrack refractor focuser.

You only have to make sure you have proper connection to your telescope to replace your stock focuser.  It will probably be either for flange ID 86 or ID 96 (that are two standard tube inner diameters for Skywatcher).

If it's ID 96 - then it is easy - you have ready made adapter:

https://www.firstlightoptics.com/baader-diamond-steeltrack-focusers/baader-steeltrack-diamond-rt-adapter-for-synta-sky-watcher-celestron-otas-with-id-97mm.html

And in the end, you only need M48 adapter:

https://www.firstlightoptics.com/baader-diamond-steeltrack-focusers/baader-diamond-steeltrack-m48-adapter.html

 

This looks like a really nice upgrade. 

A lot less expencive than a new scope, and something that will give me the best function from what I allready have :)

I will have to check the ID of the scope, and see what kind of FF I should get, If I'm not able to screw on the one I have now. 

I do belive it has threads for a filter on the nose end. Not sure if that could be used, or if the entire nose peace with the radius thing can unscrew, and show some usable treads.

 

Nice project to figure this out, and possibly get a bonus christmas present 🎅

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1 minute ago, Magnus_e said:

I do belive it has threads for a filter on the nose end.

If it does - that should be 2" filter thread - or M48. I linked suitable adapter for baader steel track focuser above. Hopefully it will have that thread and you'll be able to use it.

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8 minutes ago, vlaiv said:

If it does - that should be 2" filter thread - or M48. I linked suitable adapter for baader steel track focuser above. Hopefully it will have that thread and you'll be able to use it.

I see. Just a little slow :)

So The focuser is made for ID 86, and I need an adapter if the Equinox 80 has a ID of 96

Then the focuser https://www.firstlightoptics.com/baader-diamond-steeltrack-focusers/baader-steeltrack-diamond-rt-for-refractors.html

And the M48 adapter from the fucuser to the FF filter thread.

 

I guess if its possible to unscrew the FF nosepeace and get some threads on the body of the FF, then that is preferred? A more secure connection?

In case, just have to swap out the M48 adapter, to mate to the FF, unless that is M48 too?

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2 minutes ago, Magnus_e said:

So The focuser is made for ID 86

I think that focuser is made for some strange S88 or similar, not ID 86.

You can't attach it directly to tube with inner diameter of 86, at least I think so. In any case, you should have focuser with 96mm ID and you'll need Steeltrack to ID 96mm adapter - but again, do check.

4 minutes ago, Magnus_e said:

I guess if its possible to unscrew the FF nosepeace and get some threads on the body of the FF, then that is preferred? A more secure connection?

In case, just have to swap out the M48 adapter, to mate to the FF, unless that is M48 too?

Yes, it is better to have FF nosepiece removed as it just adds distance which can make it difficult to focus properly (nosepiece just goes inside focuser normally and does not count towards optical path).

Check if you have thread under nosepiece. I read somewhere that some FFs have nosepiece removable and that there is also M48 thread there, or it might be M54 in that model - not sure.

If it's different thread - then yes, you'll need different adapter from S58 to that thread (S58 is strange designation for steeltrack focuser thread).

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1 minute ago, vlaiv said:

I think that focuser is made for some strange S88 or similar, not ID 86.

You can't attach it directly to tube with inner diameter of 86, at least I think so. In any case, you should have focuser with 96mm ID and you'll need Steeltrack to ID 96mm adapter - but again, do check.

Yes, it is better to have FF nosepiece removed as it just adds distance which can make it difficult to focus properly (nosepiece just goes inside focuser normally and does not count towards optical path).

Check if you have thread under nosepiece. I read somewhere that some FFs have nosepiece removable and that there is also M48 thread there, or it might be M54 in that model - not sure.

If it's different thread - then yes, you'll need different adapter from S58 to that thread (S58 is strange designation for steeltrack focuser thread).

Ok. Then I have some things to doubble check, before I decide anything :)

My scope is in a remote Obsy, so I cannot just go outside and check.

With the clouds and rain here, I have time for some maintenece :)

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37 minutes ago, david_taurus83 said:

What about the Hotech SCA? They do a flattener but also a nosepiece?

https://www.firstlightoptics.com/adapters/hotech-2-sca-t-adapter.html

Only thing is 'will this be centered without tilt'?

Looks like it does not have the radius like the FF, but other than that it needs to work well with the stock focus tube and self center.

Could be and option. looks like its quality, at least.

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Looks like I did not read it all.

It does seam like it has a more advanced centering setup than most others.

"The thing just works. No matter what kind of attachment system your focuser drawtube has (single set-screw, compression ring, etc.), the device works the same. Screw your camera onto its T-threads and slide it into your drawtube. Then twist the big, black, knurled knob to compress the O-rings. Give it a few good twists and what once might have been a jiggly connection becomes rock solid. I might as well have epoxied the camera onto the focuser drawtube. Well, had I, I’d never get the camera off, but here all you do is untwist that knurled ring and then slide the camera out.

This might be worth trying first, as it's a lot cheaper than a new focuser.

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I forgot to add. Its only really suitable if your focuser is 2" for the whole length of the nosepiece. All my refractors have had a 2.5" drawtube and only the 2" adapter on the end was 2" with a compression ring so the front part of the nosepiece was in the 2.5" section! Wasn't ideal so ended up selling it.

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5 minutes ago, david_taurus83 said:

I forgot to add. Its only really suitable if your focuser is 2" for the whole length of the nosepiece. All my refractors have had a 2.5" drawtube and only the 2" adapter on the end was 2" with a compression ring so the front part of the nosepiece was in the 2.5" section! Wasn't ideal so ended up selling it.

I see. I think it might be bigger down the tube. I think I'll just send a message to FLO, they probably know.

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Hi again :)

Now I'm at my obsy location and have been checking the scope and FF.

So. I'm not sure if getting a new focuser is even possible for this scope. There is no pattern of these three screws on the circumference of where the focuser mounts to the ota.

It looks like it might be one locking screw, and then som sort of threading?

 

On the good side, the focuser tube was the same diameter for more than 50mm. (I chatted with FLO and they sad that if the focusertube was 2" for atleast 50mm, the Hotech 2" adapter would work)

Also, i tried unscrewing the nosepiese on the FF, ant that was possible. The nosepiece had threads for a 2" filter on the side that goes in to the focus tube. When I removed the nosepiece the FF had same size threads. I did try screwing in a 2" filter in the FF, and I'm 99% sure that was the correct threads. (The body of the filter and the FF stopped me from being able to attach the filter, but I'm pretty sure it was correct size threads)

 

So if the Hotech adapter has same size threads as a 2" filter, then it all should work just fine. On FLO there is not given any size for the threads. It only states that is has room for a 2" filter.

Anyone know for sure this is the same threads?

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