Field Flattener question

[Anthonyexmouth]

2 minutes ago, Alien 13 said:

I cant comment on SW scopes but found that the spacing on my WO one and FF needed to be within 0.1 mm or better, the final solution was 54 .12 mm.

Alan

how do you tune it to that degree?

[Thalestris24]

This might help (or might not!)

 

[Alien 13]

10 minutes ago, Anthonyexmouth said:

how do you tune it to that degree?

I made up spacers from anything to hand like coke cans and used a M42 to EOS adapter which is 1.1 mm thick to a 10 mm T tube that I reduced in size slightly. So I got 44 mm for the Canon distance plus the 1.1 mm for the adapter and  about 9 mm for the tube = total of 54.1 mm but a tiny bit more when measured. The coke tin spacers were used on a trial run with an 8 mm tube...

Alan

[DaveS]

These might help

Delrin spacers

But you may need to cut the ring to get it over the thread.

[Anthonyexmouth]

11 minutes ago, DaveS said:

These might help

Delrin spacers

But you may need to cut the ring to get it over the thread.

Might pick some up next time i ride past FLO.

a concern is that the pattern is the same or a little better than it was with the old thicker t ring. which means it should be even closer. this puts it well inside the 55mm. 

[Thalestris24]

What's the spacing now (sensor plane to point 1 plane (on your photo)?

 

[Anthonyexmouth]

Just now, Thalestris24 said:

What's the spacing now (sensor plane to point 1 plane (on your photo)?

 

i'll check in the morning, all covered up now. 

[Anthonyexmouth]

This is from the altair blurb

- Requires back-focus of 55mm to CCD Chip.

- For DSLRs a standard T-Thread adapter of approx. 10mm thickness is required.

[Alien 13]

I do think that you should be looking at 55 mm and trialing maybe a max of 2 mm either side...

Alan 

[Thalestris24]

1 minute ago, Anthonyexmouth said:

This is from the altair blurb

- Requires back-focus of 55mm to CCD Chip.

- For DSLRs a standard T-Thread adapter of approx. 10mm thickness is required.

Yes - should be correct providing no tilt but clip filter might interfere

[Anthonyexmouth]

5 minutes ago, Thalestris24 said:

Yes - should be correct providing no tilt but clip filter might interfere

i'll pop the original t ring on tomorrow and remove the astronomik filter. although the link you sent indicated the filter would mean adding to the distance, yet the distortion pattern indicates it needs to be closer. 

 

[Alien 13]

Experimenting with spacing is easy when you go 55 mm plus but there are not many options for going less than 55 mm without modifying existing parts.

Alan

[Thalestris24]

This person didn't have any problems with a standard t-ring:

http://www.insideastronomy.com/index.php?/topic/530-altair-lightwave-08-reducer-mini-review/

Edit: ps next time maybe take some test subs when pointing at the meridian to reduce the likelihood of tilt

[alacant]

Hi. Still too far away; or something else is wrong. Perhaps post photos of the individual components and the same in place on the telescope. Then 4 photos through the telescope.

-with and without the flattener

-with and without the filter

That may narrow our guessing a little...

Cheers

[Waldemar]

9 hours ago, Alien 13 said:

I cant comment on SW scopes but found that the spacing on my WO one and FF needed to be within 0.1 mm or better, the final solution was 54 .12 mm.

Alan

Yes... the distance can only be exactly determined by trial and error. The manufacturor stated distance is only an educated guess. 

Baader makes very nice adjustable extensions called VariLock: 
https://www.baader-planetarium.com/de/varilock-29-arretierbare-t-2-verlängerungshülse-mit-spannschlüssel-(t-2-bauteil-25y).html
a longer one is availanle as well.

[johngm]

On ‎03‎/‎03‎/‎2019 at 11:01, Anthonyexmouth said:

id read that it was a slightly better quality FF, that and it meant i could afford a click lock which makes framing easier. 

As other posters have said, it looks like you have some tilt in the optical train. Try screwing the Flattener direct to Focuser Draw tube instead of using the Click lock to see if this helps eliminate the tilt. I also have the SW ED80, and frame it by using the locking ring on the focuser tube to frame my image. Just screw the camera and flattener on as far as you can until it is fully locked onto the tube, back it off half a turn, and lock it down with the locking ring, then all you do to frame it is slacken the locking ring and move the camera and flattener to your desired frame, and when your happy, lock the locking ring in position. I hope this helps.

John

[Anthonyexmouth]

2 hours ago, Waldemar said:

Yes... the distance can only be exactly determined by trial and error. The manufacturor stated distance is only an educated guess. 

Baader makes very nice adjustable extensions called VariLock: 
https://www.baader-planetarium.com/de/varilock-29-arretierbare-t-2-verlängerungshülse-mit-spannschlüssel-(t-2-bauteil-25y).html
a longer one is availanle as well.

I don't have any space to fit one. The flattener screws directly to the T ring and it appears that it needs to be closer. 

[Anthonyexmouth]

10 hours ago, Thalestris24 said:

This person didn't have any problems with a standard t-ring:

http://www.insideastronomy.com/index.php?/topic/530-altair-lightwave-08-reducer-mini-review/

Edit: ps next time maybe take some test subs when pointing at the meridian to reduce the likelihood of tilt

Could the tilt be caused by the focuser rather than the other components? Maybe a bit of wear? I did buy it second hand. 

[Thalestris24]

1 hour ago, Anthonyexmouth said:

Could the tilt be caused by the focuser rather than the other components? Maybe a bit of wear? I did buy it second hand. 

Hi Anthony

It's possible though I don't know really. I imagine you could tell by connecting the camera using just an extension tube i.e. without the flattener. But presumably it was like that before you added the reducer/flattener? Was there any sign of tilt then?

Louise

[Anthonyexmouth]

9 minutes ago, Thalestris24 said:

Hi Anthony

It's possible though I don't know really. I imagine you could tell by connecting the camera using just an extension tube i.e. without the flattener. But presumably it was like that before you added the reducer/flattener? Was there any sign of tilt then?

Louise

Maybe, I wasn't really looking that hard. I'll post an older sub later. What parts of the distortion are tilt and what's curvature? 

Just measured the distance with both t rings. Low profile is 45mm standard looks to be 54/55. Measured from the sensor plane symbol to point 1

[Thalestris24]

2 minutes ago, Anthonyexmouth said:

Maybe, I wasn't really looking that hard. I'll post an older sub later. What parts of the distortion are tilt and what's curvature? 

Just measured the distance with both t rings. Low profile is 45mm standard looks to be 54/55. Measured from the sensor plane symbol to point 1

Hi

I think that field distortion is most apparent in/towards the corners but tilt is likely to affect just one edge or corner. When you say you 'bought it second hand' were you referring to the whole scope or to just the focuser? If the latter has been added on then maybe check the collimation eg http://philjay2000.tripod.com/usefulstuff/adventures.pdf There's lots of info online... I've never had to collimate a refractor myself. I've seen lots of posts on here where people have used CCD Inspector to good effect but it's quite expensive to buy. Maybe some kind and generous member can help out here?

Louise

[Anthonyexmouth]

The whole scope is second hand. Yeah, just looked at CCD inspector. Too expensive for me. 

[Thalestris24]

6 minutes ago, Anthonyexmouth said:

The whole scope is second hand. Yeah, just looked at CCD inspector. Too expensive for me. 

Ah, ok. Is there any obvious focuser slop or movement? Do you have an extension tube so you can use the scope without the flattener? If so, I'd go back to that and take some test subs with some pointing up to the meridian. Then you'll have a baseline. Um, is the flattener just a push fit? How it's held in could be a potential source of tilt.

Louise

[Anthonyexmouth]

1 minute ago, Thalestris24 said:

Ah, ok. Is there any obvious focuser slop or movement? Do you have an extension tube so you can use the scope without the flattener? If so, I'd go back to that and take some test subs with some pointing up to the meridian. Then you'll have a baseline. Um, is the flattener just a push fit? How it's held in could be a potential source of tilt.

Louise

Feels pretty tight and secure. 

This is the setup

[Thalestris24]

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