problem with dirt on primary showing up when imaging

[oldpink]

I've noticed it twice now when imaging esp when the software is on x5 in BYEOS with my Canon
and the same thing with my ASI on firecapture,

because I'm not 100% aligned I get a bit of drift so jupiter for instance moves across the mirror
as it moves I can see the dirt on the mirror transit the image, so I have to adjust to move the target away from the dirty part

just looking down the tube I can see a couple of cat hairs (they get everywhere) and some spots on the mirror

I know cleaning the primary is not the done thing and when viewing its not noticeable
but for imaging I think the magnification is bringing it out and causing a lot of grief and wasted time
the Jupiter image has a hair on it, and I tried to get some decent shots of the primary  so you can see for yourself
 

any suggestions

[oldpink]

better picture of the hair on the image

[IanL]

There is absolutely no possibility of the dirt or cat hair on the primary turning up in your images.  It will be so far out of focus as to be unnoticeable.

The dirt/hair/whatever it is will be on the sensor, the sensor cover glass or maybe a filter (if used and if close to the sensor).  You can use this calculator to figure out where it is:

http://www.wilmslowastro.com/software/formulae.htm#Dust

You'll need to know the pixel size of your camera (4.3 microns for the Canon), the focal ratio of your scope (f5 for the 200p) and the diameter of the dust shadow in pixels (or in this case measure the width of the hair in pixels). Assuming your first Jupiter image hasn't been resized and it is a Canon one I'm guessing it is about 5 pixels wide (if it has been resized check the original).

Plug it all in to the calculator and it will tell you roughly how far in front of the sensor the offending article is so you can clean it off (carefully).  In this case the calculator says it is 0.1mm in front of the sensor, so I'd say that points to gunk or hair on the sensor surface or more likely on front of the camera internal filter stack.  The ultrasonic cleaning usually does a good job of removing stuff, but you might need a bulb blower and to lock open the shutter and carefully see if you can dislodge the dirt (wouldn't recommend doing any more than that unless you are sure you know what you are doing).

[oldpink]

the image has been resized but I think I have tracked it down
I was convinced it was on the mirror as it happened with both camera's
but I was forgetting that the barlow & LP filter were on both as well so they will have to be checked thoroughly and cleaned if needed

thanks for putting my mind at rest, I was dreading having to take the primary out and clean it

[IanL]

the image has been resized but I think I have tracked it down

I was convinced it was on the mirror as it happened with both camera's

but I was forgetting that the barlow & LP filter were on both as well so they will have to be checked thoroughly and cleaned if needed

thanks for putting my mind at rest, I was dreading having to take the primary out and clean it

Don't forget to adjust the effective Focal Ratio for the Barlow and obviously measure the original image to get the pixel size of the offending item. Sounds like it will be one of the Barlow elements or the filter, but worth doing the calculation as you can go straight to the scene of the crime that way.

[Steve Ward]

I would say that the marks on that image are nothing to do with dirt/hairs anywhere in your optical train but are in fact stacking artifacts produced by Registax ... ! 

Try stacking the footage again using just a single "AlignPoint" and I can almost guarantee that the lines will disappear .... 

[IanL]

I assumed it was a single frame since nowhere was Registax mentioned.  Now you point it out, it does has the appearance of the classic 'crazy paving' problem which is usually due to problems with multiple alignment points in Registax.

[oldpink]

registax did make it worse, but I could see it on the laptop screen when the file was recorded
I took note of the file number so I could check it out

after careful examination I found a very small hair on the inside of my Barlow and a few spec's of dust
a couple of blasts with some dry air from a hobby air compressor seemed to deal with them

I'd like to check my optic's out to make sure they are clean before I go out again

would this work, setting up indoors and pointing the scope at a white wall and
checking all the optic's out and see if there is any more dust or hairs I have missed with the capture software

[Steve Ward]

I'd advise against using air from a compressor or a can to clean optics sir , all you will do is replace dust with oil or propellant ... 

A hand powered blower bulb is a much better bet.

What you have there are definitely stacking artifacts sir .

There may well have been a small hair on the Barlow , but unless you had exceptionally good tracking and exceptionally good seeing it would not show up on the final stacked image , as you stated you have less than perfect alignment and therefore the planet is not in the same place on the chip in any two frames therefore not lined up with the hair .... and as a consequence the hair is not stacked.

I actually use drift like this to reduce the effect of "dust bunnies" from my Solar images , the bunnies are in different places on the disc each frame and are therefore not stacked together and emphasised.

[oldpink]

its a "Clean air" system used for custom spray painting with a controlled PSI dust nozzle used to clean surfaces before painting
 

[Steve Ward]

Fair enough ... 

A bulb blower's always handy to have to hand though , and a lot more convenient than a compressor at 3am in the dark ...