Jump to content

Recommended Posts

Last night I started to take RGB of M51 with my red filter. The first frame was horrendous, it looked like the moon. Immediately after I took green frames to see if the problem re-occured, fortunately it didn't. After checking the red filter, it seemed OK, no excessive dust on it, which wouldn't account for the reflections all over the frame. I'm thinking either the red filter is loose in the mount, or the filter has just gone bad. Silly me forgot to check if the filter was secure in the mount, will need to check again, as the filter had the same result as last night. Below is a green light frame, and the red light frame, taken one after the other, both are uncalibrated. Calibrating makes no difference to the red light frame. Any thoughts?

 

Brian

 

 

Green.jpg

 

Red.jpg

Edited by AstronomyUkraine
Link to post
Share on other sites
18 hours ago, MarkAR said:

If that's not dust then something has happened to the coating on the filter. Or it's just a bit dusty and loose.

 

4 hours ago, Bob-c said:

Blimey Brian, hope you get it sorted mate.

 This is were it gets really weird. I checked the red filter yesterday, no dust on it, and it wasn't loose. It looked perfectly normal. None of the other filters are showing the same problems. Anyway, I tried the red filter out on M51 last night, same result. I slewed over to M81, took a few frames with the red filter, and it was perfect. Now I am scratching my head, this is very weird. I gave up the red filter on M51, and waited until the altitude was much higher. That did the trick, at 11.30 I switched to the red filter, and had no problems at all.

 

Here is a single light taken with the red filter at an higher altitude, and a single frame taken with the red filter two hours earlier. No imperfections at all on the light taken when M51 was higher up.

 

Red.jpg.f8399c76dc4636a13c24f1bb3217b819.thumb.jpg.9bf683094e6b1761029d6962938e1859.jpg

 

 

Whirlpool_Light_Red_gain_75_offset_NotSet_fpos_15939_c.thumb.jpg.ea51196c5a36478af86b05c5641cf93f.jpg

 

 

If anyone knows why only the red filter behaves like this at lower altitudes, I would be grateful. To me it seems there is light leaking onto the filter somewhere, but why only the red filter?

 

Brian

Link to post
Share on other sites
20 hours ago, AstronomyUkraine said:

 

 This is were it gets really weird. I checked the red filter yesterday, no dust on it, and it wasn't loose. It looked perfectly normal. None of the other filters are showing the same problems. Anyway, I tried the red filter out on M51 last night, same result. I slewed over to M81, took a few frames with the red filter, and it was perfect. Now I am scratching my head, this is very weird. I gave up the red filter on M51, and waited until the altitude was much higher. That did the trick, at 11.30 I switched to the red filter, and had no problems at all.

 

Here is a single light taken with the red filter at an higher altitude, and a single frame taken with the red filter two hours earlier. No imperfections at all on the light taken when M51 was higher up.

 

Red.jpg.f8399c76dc4636a13c24f1bb3217b819.thumb.jpg.9bf683094e6b1761029d6962938e1859.jpg

 

 

Whirlpool_Light_Red_gain_75_offset_NotSet_fpos_15939_c.thumb.jpg.ea51196c5a36478af86b05c5641cf93f.jpg

 

 

If anyone knows why only the red filter behaves like this at lower altitudes, I would be grateful. To me it seems there is light leaking onto the filter somewhere, but why only the red filter?

 

Brian

I don't think it is dust Brian, as it would not all disappear completely like that. My thinking is some form of condensation maybe causing  it.. or a corrupt file or something on those lines, never seen this type of interference on a filter before. Hope you can get it tracked down and all sorted.

 

Bob.

Link to post
Share on other sites
2 hours ago, Bob-c said:

I don't think it is dust Brian, as it would not all disappear completely like that. My thinking is some form of condensation maybe causing  it.. or a corrupt file or something on those lines, never seen this type of interference on a filter before. Hope you can get it tracked down and all sorted.

 

Bob.

I have no idea Bob, but if it was condensation it would have shown up when I took an image of M81, just a minute or two after the first image of M51. If the red works when at a higher altitude I can cope with that. I'm going to replace it with a higher quality Baader filter just to be sure.

 

Brian

  • Like 1
Link to post
Share on other sites
6 hours ago, AstronomyUkraine said:

I have no idea Bob, but if it was condensation it would have shown up when I took an image of M81, just a minute or two after the first image of M51. If the red works when at a higher altitude I can cope with that. I'm going to replace it with a higher quality Baader filter just to be sure.

 

Brian

Will be interesting to see if it is the filter Brian.

 

BOB.

Link to post
Share on other sites

To me it looks like a high level of background light at lower elevation has highlighted the dust and bits in the imaging train (much like a Flat frame). Infra red security lights can do all sorts of strange things. The spoilt frames have a matched distortion pattern, have you compared them to your Red Light frame?

  • Like 2
Link to post
Share on other sites
33 minutes ago, MartinS said:

To me it looks like a high level of background light at lower elevation has highlighted the dust and bits in the imaging train (much like a Flat frame). Infra red security lights can do all sorts of strange things. The spoilt frames have a matched distortion pattern, have you compared them to your Red Light frame?

I agree with you. I never have this problem shooting NB light frames. The problem disappears towards the Zenith.

Link to post
Share on other sites

I don’t think the 1600MM has a IR/UV cut filter on the sensor window from memory. I’ve recently sold mine but seem to recall that. So it may of course be IR light. But as the dark patches seem similarly shaped also in the same positions on both frames and the scope has moved between frames, I can’t see it coming from a fixed object on the ground. It may be moving with the mount - maybe an LED, mount power LED?, leaking into the filter wheel.Try putting black tape around the cover plate of the EFW to rule that out as it might be coming from another source.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...