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Likwid    5

Hello,

I am new to Astrophotography and I have posted a few questions already. I am using an Orion ST80 with a Skywatcher Star Adventurer and I am getting decent results. I have a Tamron 150-600 for my normal photography and I decided to attach it and take a test shot. I wasn't concerned about the weight of the lens as I have a balanced counterweight kit with it. I am imaging with a Rebel XS that I modded myself and removed the IR/Cut filter and I am also using BackyardEOS to control everything. I tried 5 test shots and stacked them in DSS (I think 90 seconds) and some strange black orbs showed up in my frame in the upper right. It happened to a few different frames so it wasn't a fluke. It is on the originals also before I stacked. I don't use this lens very often and I am very careful with the caps so I doubt any dust is in it. I took shots of the eclipse with it (With an Orion Solar Filter) and the night before before I took shots of the moon and they all came out normal. I also took normal test shots after during the day and they seemed normal also. I'll see if I can find the original image, but this is after editing trying to get them out. Thanks in advance for any help!

36553517590_89926cf4df_o.jpg

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RichM63    3,068

Water spot stains spring to mind. They are not just top right, but all over the image if you look closely.

Rule out the camera and sensor dust etc by taking some shots against a dark background with a different lens. A bright background could easily mask them.

I don't seem to have dust ingress into either of my big Tamrons they are pretty well sealed IMHO.

Of course they could be something else entirely.

Rich

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happy-kat    2,952

Check out if you can see them on a single frame.

Edit: To rule out stacking artifacts.

Edited by happy-kat

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Alien 13    3,307

The marks are near to the sensor but dont look like they are on it (they would be in focus) but I could be wrong, did you have a clip in filter fitted? I would also look at the end of the Tamron lens.

Alan

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Likwid    5

Thanks for the replies! No clip in filter, just full spectrum currently. I have been using this camera the last few nights and it seems to be isolated just to this lens so far. I was imaging Andromeda (Or trying to at least) with my ST80 and this camera 2 nights later and there are no artifacts in the images. Water spots is a good call, I may have not seen them when I checked the UV Filter that is protecting the lens. I'll give the lens a good cleaning when I get home from work and report back, thank you for the replies! I was worried that my lens was damaged.

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Astronator    25

I've experienced this several times before. Have you tried the simplest yet? Sensor clean of camera and clean the lens both in the front and back.

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StuartJPP    4,517

It certainly isn't something on the front of the lens, it could (but I doubt it) be on the back elements of the lens. But most likely it is on the sensor.

Stop the lens down to its smallest aperture (f/32 or whatever) and point the camera to either a bright light or the sky or even a white or evenly illuminated wall and take an image. The dust bunnies should be much more defined.

Edited by StuartJPP
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Likwid    5

That is very odd. Individual frames from that night had the spots. I did a manual sensor cleaning to check the sensor and it was fine (I removed the IR/Cut Filter recently and it was incredibly clean then). The camera end of the Tamron was clean also but the UV Filter on the other end had some dust on it, nothing that would cause the artifacts though. I just used a blower and blew everything off and took a few test frames, one was pointed at the wall and I left the shutter open for 30 seconds and nothing came up. I took a few other random shots and everything seemed perfectly normal. That is incredibly odd. I guess I will take it out on the next clear night and hopefully I don't have the same issue again. Thank you for the responses everyone!

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Alien 13    3,307

I have had spots on my sensor that were almost invisible and only showed up under UV light (a blue LED will work) so its worth checking.

Alan

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Likwid    5

Thanks Alan. I checked the sensor with a UV flashlight and it was perfectly clear, the end of the lens that connects to the body was clean also. I checked the UV Filter protecting the front element and it was pretty dusty. It must have gotten dirty and I couldn't see it without the flashlight. I cleaned that off really well and the front element itself was pristine. It was probably just the filter and the particles came out in the really long exposure and not with the faster shutter speeds. I think it will be clear tonight so I should know by tomorrow if that worked! Thank you everyone again!

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