Field Flattener question

[david_taurus83]

What's the knurled ring and the spacer just before the t-ring? It doesnt look like the advertised 0.8 flattener?

[Thalestris24]

51 minutes ago, david_taurus83 said:

What's the knurled ring and the spacer just before the t-ring? It doesnt look like the advertised 0.8 flattener?

It's just the end with the thread - I think they must have changed the design from a smooth finish to a knurled one. Mine is the same as Anthony's

Louise

[Anthonyexmouth]

1 hour ago, Thalestris24 said:

Hi again

I've no experience of either Baader clicklocks, or the ED80, but looking at your pic I wonder why there is thread showing at the ed80 end - is that normal? FLO's pic doesn't show any thread? https://www.firstlightoptics.com/adapters/baader-click-lock-2956256-m56-celestron-skywatcher.html
Also (it might be a trick of the light - or my eyes!) is there a gap between the reducer and the clicklock? Plus, I take it you lock the focus tube somehow? Maybe, if all else fails you could go back to the original thumbscrew fitting, just to test? I'm just thinking out loud, so to speak

Louise

 

I took the whole SW adapter off, looks like they left the small ring on to cover the last of the thread, doesn't do anything. I could put it back to make it look better. The flattener has a little shoulder that keeps it back a couple of mm but it's tight against it

[Anthonyexmouth]

Ok, you shamed me into finding the ring and putting it back.

[Thalestris24]

33 minutes ago, Anthonyexmouth said:

I took the whole SW adapter off, looks like they left the small ring on to cover the last of the thread, doesn't do anything. I could put it back to make it look better. The flattener has a little shoulder that keeps it back a couple of mm but it's tight against it

Hmm… I'm still a bit suspicious of the gap... I'm also suspicious of your t-ring - it looks like one of the little grub screws is missing? T-rings can be a pain if the inner ring is loose or not well fitted.

Louise

[Anthonyexmouth]

2 hours ago, Thalestris24 said:

Hi again

I've no experience of either Baader clicklocks, or the ED80, but looking at your pic I wonder why there is thread showing at the ed80 end - is that normal? FLO's pic doesn't show any thread? https://www.firstlightoptics.com/adapters/baader-click-lock-2956256-m56-celestron-skywatcher.html
Also (it might be a trick of the light - or my eyes!) is there a gap between the reducer and the clicklock? Plus, I take it you lock the focus tube somehow? Maybe, if all else fails you could go back to the original thumbscrew fitting, just to test? I'm just thinking out loud, so to speak

Louise

 

I took the whole SW adapter off, looks like they left the small ring on to cover the last of the thread, doesn't do anything. I could put it back to make it look better. The flattener has a little shoulder that keeps it back a couple of mm but it's tight against it

[Anthonyexmouth]

All the grub screws are in the t ring

[Anthonyexmouth]

OK, heres 2 subs from tonight. different targets but the leo triplet is with the flattener and the other without the flattener. didn't do any more because i got too cold. 

 

 

[Thalestris24]

Was that with the standard t-ring? The stars look generally a bit eggy in the first one which I doubt have anything to do with the flattener, plus any tilt isn't obvious to me - at least, not along the bottom. There is some field distortion but that would be fixed with spacing or maybe no clip filter. The second one looks as expected, I think. Ideally, you want to compare like with like - same target, exposure and orientation.

Louise

[Anthonyexmouth]

3 minutes ago, Thalestris24 said:

Was that with the standard t-ring? The stars look generally a bit eggy in the first one which I doubt have anything to do with the flattener, plus any tilt isn't obvious to me - at least, not along the bottom. There is some field distortion but that would be fixed with spacing or maybe no clip filter. The second one looks as expected, I think. Ideally, you want to compare like with like - same target, exposure and orientation.

Louise

yeah, the standard t ring. i'll try again tomorrow night before it gets too cold out. both are 3 min subs

[Alien 13]

I have never trusted EOS to T adapters with a DSLR because of the inner ring held by 3 screws, I allways use these now.

Together they make the 11 mm of the standard ring and although they have different thread pitches they do fit together (once).

Alan

[michael8554]

Try short exposures at high ISO so guiding errors don't feature.

Same target, something with lots of stars !

There is coma in the second image, no coma corrector.

The first image, with corrector,  is over corrected, suggests the spacing is too much.

Michael

[Anthonyexmouth]

6 minutes ago, michael8554 said:

Try short exposures at high ISO so guiding errors don't feature.

Same target, something with lots of stars !

There is coma in the second image, no coma corrector.

The first image, with corrector,  is over corrected, suggests the spacing is too much.

Michael

thats what the original thought was, i changed to a low profile t ring but even when the spacing was reduced by 9/10 mm it still looked too far away but the distance was 44mm. 

[michael8554]

And maybe a shot with an extra 2 to 5mm of spacing (if you have one) so we can really see the effect of too much spacing ?

Michael

[Thalestris24]

6 minutes ago, Anthonyexmouth said:

thats what the original thought was, i changed to a low profile t ring but even when the spacing was reduced by 9/10 mm it still looked too far away but the distance was 44mm. 

I reckon with the standard t-ring but no filter you may be ok. If that's the case then filter+low profile t-ring+spacer (to correct distance) should work.

[Waldemar]

8 hours ago, michael8554 said:

Try short exposures at high ISO so guiding errors don't feature.

Same target, something with lots of stars !

There is coma in the second image, no coma corrector.

The first image, with corrector,  is over corrected, suggests the spacing is too much.

Michael

Good advice. I like to add:

Don't forget if using a filter, 1/3 of the filter thickness needs to be added to the light path, so the actual distance has to be shorter.

The left side of both images is the most distorted. To me that means something is tilted. The way to find out what, is to rotate first the complete camera setup in the telescope and then the different pieces one by one (if at all possible). Don't forget, the lenscell maybe out of collimation as well...
If rotating the whole camera set up does not change anything, then the lenscell is the culprit. (for the tilt issue, that is...)

[alacant]

8 hours ago, Anthonyexmouth said:

different targets

Hi. Keep the same target, same exposure with and without the ff and with and without the filter. Next change to the low profile and repeat. It's gonna be 2 clear nights lost:(

Or go along to an astro club and get someone (everyone is an expert at astro clubs!) to come over and sort it out for you. That has the advantage of being able to check the ff on another telescope.

Or forget the ff and correct the aberrations in software.

Cheers and good luck.

[Anthonyexmouth]

Looks like it's gonna be clear tonight so I'll try and rattle off a couple of short subs with and without the FF and both standard and low profile t ring. I might do them all.

If it looks like I've got time and it's not too cold I'll do with and without filter. 

[Thalestris24]

24 minutes ago, Anthonyexmouth said:

Looks like it's gonna be clear tonight so I'll try and rattle off a couple of short subs with and without the FF and both standard and low profile t ring. I might do them all.

If it looks like I've got time and it's not too cold I'll do with and without filter. 

That's good. I wouldn't bother wasting your time with a low profile t-ring unless you have spacers to add to bring it up to near the standard t-ring distance. With the standard t-ring and no filter, I think it might work ok.

Louise 

[Anthonyexmouth]

I hope so. Hoping it's an easy fix. Losing the enthusiasm I had to buy a new camera until I sort this out. 

[Anthonyexmouth]

ok, freezing out, maybe iv'e been in the sun too long today. Heres a 15 sec ISO 1600 sub . Standard T Ring/ No LP Filter/ With FF/R

[Thalestris24]

Hi

Unfortunately, the pattern suggests the flattener is too far from the  sensor  I really hoped it would be ok without the filter.

I know altair astro sell the Lightwave flattener packaged with a t-ring but don't know whether that has a slightly different size or whether the depth of t-rings varies much. If it does then someone else must have had the same experiences. Maybe post a separate question about using the flattener.

[Anthonyexmouth]

Just now, Thalestris24 said:

Hi

Unfortunately, the pattern suggests the flattener is too far from the  sensor  I really hoped it would be ok without the filter.

I know altair astro sell the Lightwave flattener packaged with a t-ring but don't know whether that has a slightly different size or whether the depth of t-rings varies much. If it does then someone else must have had the same experiences. Maybe post a separate question about using the flattener.

those are the pics iv'e been looking at. but getting the same pattern with the low profile t ring too. 

[Thalestris24]

5 minutes ago, Anthonyexmouth said:

those are the pics iv'e been looking at. but getting the same pattern with the low profile t ring too. 

Hmm… that doesn't make sense... Have you got a digital caliper? They are really useful for checking spacings etc Just wondering whether you really need the optional canon m48 t-ring kit https://www.altairastro.com/canon-dslr-0.8x-reducer-flattener-kit-for-starwave-70ed-f6-refractor.html It looks to me that maybe the optional t-ring fits in place of the bit that screws on the end of the flattener i.e. the knurled ring. That would make sense as it would reduce the sensor distance significantly. If that is actually the case then altair astro are guilty of not making it clear!

Louise

[Anthonyexmouth]

8 minutes ago, Thalestris24 said:

Hmm… that doesn't make sense... Have you got a digital caliper? They are really useful for checking spacings etc Just wondering whether you really need the optional canon m48 t-ring kit https://www.altairastro.com/canon-dslr-0.8x-reducer-flattener-kit-for-starwave-70ed-f6-refractor.html It looks to me that maybe the optional t-ring fits in place of the bit that screws on the end of the flattener i.e. the knurled ring. That would make sense as it would reduce the sensor distance significantly. If that is actually the case then altair astro are guilty of not making it clear!

Louise

i looked at those, but was given the impression they are designed for the starwave ota and the one i got is a more generic one for slightly longer focal length scopes like the ED80 at f7.5. the kit is really just what i have with a canon T Ring added.