SCT C11 Imagine disaster

[Tinker1947]

I have been using the C11 for a month or 2 but imagine wise not to often, it has produced some clear clean images but the last week or so its gone down hill, this image of Mizar taken with a Canon 1100D straight into the back of the C11 i had to use a Baader Coma Corrector for the connection i have a f6.3 Focal reducer get the same results so this is with the least amount of kit in the imagine train, the internals of the scope look clean, the secondary mirror spotless, the primary just a few smudgy type marks very faint, the scope is 4 month old and has never had the corrector plate removed....800iso, 180 seconds, 10 or so subs, guided nice straight PHD graph...

[Leveye]

Looks like dirty optics, condensation and some light leaking in from somewhere. Was there a laptop close by? Time to clean house!

[Uplooker]

Amazing what a bit dew on the correct plate when magnified.

Ian

[brantuk]

Try with a dew band on the corrector plate. The atmosphere has become very moist these last few nights. That's my guess.

[Tinker1947]

Looks like dirty optics, condensation and some light leaking in from somewhere. Was there a laptop close by? Time to clean house!

The Optics , the secondary when removed is like brand new no marks or dust, the primary has a few marks that can only be seen with a torch very faint stain like marks properly damp from being  out in the Obby all winter......

[Tinker1947]

Amazing what a bit dew on the correct plate when magnified.

Ian

The scope has a Astrozap heater shiled with another dew band round the outside of this, both running on 13.8 volt, there warm to touch, the corrector plate is clean and dry just to odd speck of dust, they blow off with the hairdryer....

[Tinker1947]

Try with a dew band on the corrector plate. The atmosphere has become very moist these last few nights. That's my guess.

As i typed. it has 2 dewbands that appear to do a good job....

[JamesF]

Definitely looks like there's some dust specks somewhere, but there are other things I don't understand that might be sensible to work on first, such as how all that light is getting around the edges of the sensor, and why the stars have diffraction spikes.  There's also a slightly curved shadow from around 1/3rd of the way along the top edge from the left down to the star on the left edge.  There was absolutely nothing but open sky in front of the corrector plate when you took this image?

James

[Tinker1947]

Definitely looks like there's some dust specks somewhere, but there are other things I don't understand that might be sensible to work on first, such as how all that light is getting around the edges of the sensor, and why the stars have diffraction spikes.  There's also a slightly curved shadow from around 1/3rd of the way along the top edge from the left down to the star on the left edge.  There was absolutely nothing but open sky in front of the corrector plate when you took this image?

James

i don't mind taking the corrector plate out and giving the optics a clean, the scope is 4 or 5 months old the corrector plate has never been taken out the secondary mirror had been out with the scope level so nothing dropped inside, as for the light getting round the edge of the sensor i can't think how, there's a 3.25" visual back on the scope then the 1100D attached so no light there, Astrozap on the front, and when the image was taken the moon was 90 degrees off to the right, no light in the direction the scope was pointing, If ti come to cleaning the optic how is the primary dealt with i don't fancy taking it out, so how would it be cleaned, the corrector plate would come out and go back the same way, i would also flock the inside if this cleaning option is required....

How the 1100D is attached...

The Dewshield...

[JamesF]

I suspect whatever has the dust on it is fairly close to the camera.

Can you turn the camera relative to the CC and see if the dust specks move?  Then turn the CC relative to the OTA and see if they move?

James

[Steve Ward]

Too close to focus to be the scope , I'd say the sensor or reducer needs a clean myself.

The light is probably leaking in from behind through the viewfinder if anywhere , you'll find there's a blanking plug for it attached to the neckstrap ... 

[ChrisLX200]

The appearance of the spots in the image suggest they are very close to the sensor (if not actually on it) because they are relatively small, I would also suggest they are not on the main optics of the scope at all. Is there a Clip filter in the camera? The vignetting is to be expected on a DSLR sensor because of the reducer, although why the outer parts are light instead of dark is a mystery - more suggestive of internal reflections in the outer parts of the optical train (or maybe light leaking in from somewhere else?)  It's not likely perhaps but is the inside of the camera or the rear-most element of the reducer getting misted up? (the fact you have a mixture of light and dark donuts suggests there is mist on some element near the sensor, together with dust motes on at least 2 surfaces). That's my 2p's worth anyway

ChrisH

[Zakalwe]

Cover the viewfinder of the camera. Light can enter the VF and it will spoil long exposures. I found this out the hard way after an LED on a power brick ruined a set of subs once.

[Tinker1947]

I suspect whatever has the dust on it is fairly close to the camera.

Can you turn the camera relative to the CC and see if the dust specks move?  Then turn the CC relative to the OTA and see if they move?

James

I will give that a try, bit misty at the moment, i did look at the 1100D Sensor looks spotless, I also took the visual back off and checked it for spiders webs ect...

[Tinker1947]

Cover the viewfinder of the camera. Light can enter the VF and it will spoil long exposures. I found this out the hard way after an LED on a power brick ruined a set of subs once.

Will do this i have a blank thingy to cover it.....

[Tinker1947]

Too close to focus to be the scope , I'd say the sensor or reducer needs a clean myself.

The light is probably leaking in from behind through the viewfinder if anywhere , you'll find there's a blanking plug for it attached to the neckstrap ... 

It did the same produce the same type of image with the FR attached, this image is just the DSLR attached to the visual back, so there is just air between the secondary and the dslr sensor...i will try the viewfinder blank.....

[JamesF]

It is surprising how small a particle of dust can be and still look huge on the sensor.  A speck that covers a 20x20 area of pixels for instance and looks like someone has dropped a brick on the sensor will still only be 0.1mm across.

James

[Tinker1947]

The appearance of the spots in the image suggest they are very close to the sensor (if not actually on it) because they are relatively small, I would also suggest they are not on the main optics of the scope at all. Is there a Clip filter in the camera? The vignetting is to be expected on a DSLR sensor because of the reducer, although why the outer parts are light instead of dark is a mystery - more suggestive of internal reflections in the outer parts of the optical train (or maybe light leaking in from somewhere else?)  It's not likely perhaps but is the inside of the camera or the rear-most element of the reducer getting misted up? (the fact you have a mixture of light and dark donuts suggests there is mist on some element near the sensor, together with dust motes on at least 2 surfaces). That's my 2p's worth anyway

ChrisH

Ok on the spots on the sensor i look at the sensor with liveview on and no lens attached appeared spotless, i will give it a puff with rubber puffer i have, no clip filter used just air between the sensor and the secondary with this image, all parts with glass are given a blow with the hairdryer before there attached although with the dslr and this image there's just air between the sensor and secondary, i did get the same result when i used the FR....i have a Nikon D80 thats i used for imagine i will try that when the mist clears or clouds clear....

[Tinker1947]

It is surprising how small a particle of dust can be and still look huge on the sensor.  A speck that covers a 20x20 area of pixels for instance and looks like someone has dropped a brick on the sensor will still only be 0.1mm across.

James

I will stick the Nikon D80 on there when its next clear....

[Tinker1947]

Half opened the roof to get a bit of sun on the scope, weather permitting i will align it in the same direction (Ursa Major) and use the Nikon D80 if thats sorted the problem, i can  see a Canon 600D astro modded arriving next week, if not some flocking and cleaning bits as SGL members recommend.

The mobile phone used i noticed a blemish or 2 in this image, it taken through my Office/Space DG window....nothing to do with the Canon...

 

[Tinker1947]

Well its a full Moon, loads of cloud, so i set-up and took another set of imgines, couple of things went wrong, i used a nikon D80, but forgot to alter the ISO to 800 it is at 100, and never alter the image type so there jpegs, anyways around 10 subs at iso100 X 180 seconds  NO Darks,Flats or Bias, and the end result is much the same as the reason for this thread, it would seem its the scope and not the Canon 1100D,  thoughts...anybody...

 

[jambouk]

If you do darks and flats does it all go away?

If nothing on the corrector plate, on the primary or on the secondary, and nothing sitting in the light path, then no idea. Is the focal reducer clean?

Hope you get it sorted.

Jd

[Tinker1947]

If you do darks and flats does it all go away?

If nothing on the corrector plate, on the primary or on the secondary, and nothing sitting in the light path, then no idea. Is the focal reducer clean?

Hope you get it sorted.

Jd

No Focal Reducer, only air between the DSLR Sensor and the Secondary....

[JamesF]

I'm not 100% convinced it's the same set of dust spots.  I can't see any obvious patterns in the image from the Nikon that are also present on the Canon image.

Have you tried rotating the camera between two subs yet?

James

[Tinker1947]

I'm not 100% convinced it's the same set of dust spots.  I can't see any obvious patterns in the image from the Nikon that are also present on the Canon image.

Have you tried rotating the camera between two subs yet?

James

No James it came over cloudy so i put it all away, i have ordered from various places, Flocking (FLO), camel hair brushes, Iso/Alcohol, Distilled Water, Microfiber Clothes, Baader cleaning fluid and cloth (FLO) I did when the weather was really wet for a bit get a fungus growth on the Obby Roof i am wondering if some of the spores may have taken to the Primary Mirror, when all me cleaning stuff has landed i will strip it down and give it a good clean, Primary, Secondary, regrease and flock, if that fails i will use the 10" Newt....

If its clear Sunday night i will try the 1100D and alter the angle ect...