Explore scientific field flattner problem

[Blackrose]

Hello Stargazers,

 

I have an Explore scientific ED80. I also bought a dedicated flattner sold by the explore scientific. At the beginning the performance was great. But now I have getting very bad and curved field and stars. I really don't understand what happened in between. I took the flattner and camera apart for visual viewing and then when I assembled the same setup together it's not performing anymore. I'll add before and after pictures. It would be appreciated if you could help. Thanks in advance,

 

CS and cheers,

 

Kamyar

 

PS: Andromeda is before and Iris nebula is after the fact.

[david_taurus83]

Hi. Even the M31 image has some funky star shapes towards the edge of the field but that could be the limitation of the flattener. The Iris is a lot worse. What camera do you use and have you got the correct/recommended spacing from the FF to the sensor?

[Blackrose]

1 minute ago, david_taurus83 said:

Hi. Even the M31 image has some funky star shapes towards the edge of the field but that could be the limitation of the flattener. The Iris is a lot worse. What camera do you use and have you got the correct/recommended spacing from the FF to the sensor?

First, I know M31 is bad, but at least it's better than the Iris. That's the problem which I want to figure out at the moment. To get the best possible result.

Second, I am actually first time hearing about such a thing. I didn't know spacing. Would you elaborate? I have Nikon D800 T2 ring attacked to the FF.

[david_taurus83]

Field flatteners work at an optimal spacing from the lense element to the camera sensor. What flattener do you have?

[Blackrose]

40 minutes ago, david_taurus83 said:

Field flatteners work at an optimal spacing from the lense element to the camera sensor. What flattener do you have?

This one from ES. https://www.bresser.de/Astronomie/Zubehoer/Korrektoren-Reducer/EXPLORE-SCIENTIFIC-MPCC-Field-Flatt-ED-APO-NikonT2.html

 

How do I change the distance between ff and camera sensor? Do I need a spacer of sorts? What is the name if yes?

[david_taurus83]

It seems to be a general purpose FF and I can't see much technical info listed for it either. Might be worth an email to Bresser customer services and ask them what the optimal spacing is. For example, the Baader MPCC has a recommended distance of 55mm +/-1mm from element to sensor. That's the info you need. You can then work out what you need to introduce, if anything, to improve. In your first image it's not too far off. You could make some shims out of a tin can, for example, and fit them over the thread in between FF and T ring, and perform some tests. Or you can buy some delrin spacers for the same purpose. Though, £12/15 for a bag of small plastic rings is a rip off imo...

 

You say you took the flattener apart? Apart as in removed the lense? If so, have you put it back in the correct way?

[david_taurus83]

Found this over on Cloudy Nights. It's suggested as 45mm from the flatteners flange to sensor. Do you know what the depth from your cameras mating face to sensor is?

 

https://www.cloudynights.com/topic/606724-es-ed80-w-flattener-spacing/

 

Edit: Just looked up the D800. That sensor is massive! Even with the correct spacing you may well not be able to fully correct the field right to the edges..

[Blackrose]

 

 

3 hours ago, david_taurus83 said:

It seems to be a general purpose FF and I can't see much technical info listed for it either. Might be worth an email to Bresser customer services and ask them what the optimal spacing is. For example, the Baader MPCC has a recommended distance of 55mm +/-1mm from element to sensor. That's the info you need. You can then work out what you need to introduce, if anything, to improve. In your first image it's not too far off. You could make some shims out of a tin can, for example, and fit them over the thread in between FF and T ring, and perform some tests. Or you can buy some delrin spacers for the same purpose. Though, £12/15 for a bag of small plastic rings is a rip off imo...

 

You say you took the flattener apart? Apart as in removed the lense? If so, have you put it back in the correct way?

It's rather my bad English. What I meant is I dismounted the flattner and camera to do visuals and then went for imaging again.

[Blackrose]

3 hours ago, david_taurus83 said:

Found this over on Cloudy Nights. It's suggested as 45mm from the flatteners flange to sensor. Do you know what the depth from your cameras mating face to sensor is?

 

https://www.cloudynights.com/topic/606724-es-ed80-w-flattener-spacing/

 

Edit: Just looked up the D800. That sensor is massive! Even with the correct spacing you may well not be able to fully correct the field right to the edges..

exactly that's what I thought. That's why I'm ok with the Andromeda result. I don't think I'm ever gonna get better than that. But who cares  there are a lot of pixels so some of them could be cropped out.

 

Flange is 46.5 AFAIK.

[michael8554]

Both images look the same to me in the middle of frame - out of focus.

Michael 

[alacant]

22 hours ago, Blackrose said:

It would be appreciated if you could hel

Hi. According to the CN thread it needs 55mm (seems too short to me; my tsflat is ~120mm) from the shoulder of the ff where the thread stops to the camera sensor. The low profile t-adaptor gives you only 2mm extra. If you're using a dslr, you're gonna need an 8mm extension. e-mail Bresser. They usually reply immediately.

HTH.