#1  
Old 12-06-2008, 10:57 PM
darrellx's Avatar
darrellx (Darrell)
Registered User

darrellx is offline
 
Join Date: Dec 2007
Location: Gold Coast, Queensland
Posts: 278
DNK21 and "dirt"

Guys
I have recently purchased a DMK21 and have now tried to use it with both a PowerMate5x and a 2x Barlow. Generally I am extremely happy with what I have already done, but I have come up with one small problem.

With the 2x barlow, I don't notice any problems, but with the 5x I see these dark blotches in the field. I figure these blotches must be on the lens or the ccd. As I moved the view around, the blotches stayed on the same spot on the screen.

I have attached two images. This is my second attempt at imaging, and I used the 5x. output000 has two rather large dark spots. Jupiter 3 is the processed image using Registax.

Over the whole field of view, there are quite a few of these spots of varying size. When I play the AVI, these blotches stay in place for the duration.

I have used a blower brush on the ccd and the 5x, but the spots are still there (but maybe fewer of them).

So, should I be blowing harder? Should I be using a cotton bud with some distilled water? Which do you think is the most likely source of the spots - ccd or lens? What would the blotches most likely be? Both are new and this is the first time I have tried them.

Thanks
Darrell
By the way, I am using all this on a Skywatcher 8 inch with an EQ5 mount.
Attached Thumbnails
Click for full-size image (Jupiter 3 - auto2.jpg)
30.1 KB20 views
Click for full-size image (outputq000.jpg)
64.1 KB25 views
Reply With Quote
  #2  
Old 12-06-2008, 11:39 PM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Brisbane, Australia
Posts: 6,708
I have one similar on my ToUcam... (without any lens or filter, it has to be on my CCD... I have NFI what to do, but just letting you know you're not alone...
Reply With Quote
  #3  
Old 13-06-2008, 04:01 AM
iceman's Avatar
iceman (Mike)
Sir Post a Lot!

iceman is offline
 
Join Date: Sep 2004
Location: Gosford, NSW, Australia
Posts: 36,709
Sounds like it's a dust mote or two. I get them fairly regularly on my DMK as well, especially when changing it between barlows or using it as a guide camera then back to an imaging camera etc.

To clean, I use a q-tip dipped in demineralised water, wiping it across the face of the CCD from one side tot he other in strokes.

I then sit it vertical so the water slides/dries off the side. This usually gets rid of all the dust for me.

Sometimes the water doesn't completely slide off and it ends up worse than when I started, so I just do it again.
Reply With Quote
  #4  
Old 14-06-2008, 01:09 AM
rsbfoto's Avatar
rsbfoto
Registered User

rsbfoto is offline
 
Join Date: Dec 2006
Location: Mexico City
Posts: 106
Quote:
Originally Posted by iceman View Post
Sounds like it's a dust mote or two. I get them fairly regularly on my DMK as well, especially when changing it between barlows or using it as a guide camera then back to an imaging camera etc.

To clean, I use a q-tip dipped in demineralised water, wiping it across the face of the CCD from one side tot he other in strokes.

I then sit it vertical so the water slides/dries off the side. This usually gets rid of all the dust for me.

Sometimes the water doesn't completely slide off and it ends up worse than when I started, so I just do it again.
Hi,

I think water even distilled water is not a good idea. I use 99.999% pure isopropyl alcohol with 10% ether. This dries away wothout leaving any trace on the chip.
Reply With Quote
  #5  
Old 14-06-2008, 01:42 AM
AlexN's Avatar
AlexN
Tunnel Vision

AlexN is offline
 
Join Date: Mar 2008
Location: Brisbane, Australia
Posts: 6,708
mm i was considering Isopro..
Reply With Quote
  #6  
Old 14-06-2008, 12:55 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
Dust bunnies

Isopropyl is the way to go, if a can of compressed air doesn't move them. The blower brushes are NBG, they just seem to spead any dust!
I'm using Lucam to drive the DMK. Try doing some flats ( point the scope a a bright sky with a white T shirt over the objective) then using RegistaxV4 you can use the flat to remove the dust bunnies.
My problem is a bit different... using the DMK with the SM40/ PST for solar work.... how do you take flats in Ha ????????
Reply With Quote
  #7  
Old 14-06-2008, 01:11 PM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Even though the brush is a bit big, I swear by the Arctic Butterfly. Works an absolute treat!! No fluids to muck around with. (search around you can get them cheaper.)
Reply With Quote
  #8  
Old 16-06-2008, 08:09 AM
rsbfoto's Avatar
rsbfoto
Registered User

rsbfoto is offline
 
Join Date: Dec 2006
Location: Mexico City
Posts: 106
Quote:
Originally Posted by Merlin66 View Post
My problem is a bit different... using the DMK with the SM40/ PST for solar work.... how do you take flats in Ha ????????
You do not need to take the flats with the filter on. Take off the filter and take normal DSO flats. This will take away your dust bunnies from you Solar H-Alpha images.
Reply With Quote
  #9  
Old 16-06-2008, 08:42 AM
sheeny's Avatar
sheeny (Al)
Spam Hunter

sheeny is offline
 
Join Date: Jun 2005
Location: Oberon NSW
Posts: 12,688
Quote:
Originally Posted by [1ponders] View Post
Even though the brush is a bit big, I swear by the Arctic Butterfly. Works an absolute treat!! No fluids to muck around with. (search around you can get them cheaper.)
I agree whole heartedly! I held off buying one because they aren't cheap, but when I couldn't get the dust off by all the other methods, I bought one, and on first use it cleaned the sensor perfectly! No fuss! Brilliant bit of kit!

Al.
Reply With Quote
  #10  
Old 16-06-2008, 02:53 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
rbsfoto,
There's no filter to remove when viewing the Sun in Ha... it's part of the optical system; not like DSO stuf.

I agree if it's only the dust bunnies, but what about the flat field? There's possibly some vignetting in the system, this will not be corrected??
I was under the impression that all flats should be taken with the camera/ optical system which will take the lights??
Someone suggested rotating the camera and doing a median average????

Last edited by Merlin66; 16-06-2008 at 02:55 PM. Reason: added comment about fixed Ha filters
Reply With Quote
  #11  
Old 16-06-2008, 03:19 PM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Where are you bunnies Ken? On the chip or in the scope?

Trying to do separate avi and rotating the camera will cause a few issues even though it should take care of the bunnies, namely the features on the sun may have morphed to much between avi runs to be able to get a good clear result. What you might want to do is to dither your avi. Move your mount about the diameter of the largest bunny in RA and then in Dec a number of times over the Avi imaging run. Just make sure that you let it settle for a few seconds between dithering movements. Then split the Avi into bmps and when you combine the bitmaps see if you are able to use a median combine (not sure if Registax will let you use a median combine but you could using IP and possibly K3). Theoretically this should take care of your bunnies and possibly even help with the vignetting as well.
Reply With Quote
  #12  
Old 16-06-2008, 03:35 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
The dust is on the chip.
I've already tried to take some flats with the PST just pointing of the Sun's disk ( to get enough light!!) this is good enough to get rid of the bunnies, but adds a series of graduated "circles"/ gradient to the image!!!!
The "sweet spot" of the PST is also a problem with flats; they seem to accentuate the problem!!
Reply With Quote
  #13  
Old 16-06-2008, 03:42 PM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
Yes I can imagine you would get an interference type newtonian rings pattern (can I use all those words together like that ) if you tried that. Anyway to place a diffusing type screen in front of the pst but far enough away that it wont create its own problem? Sort of like a dome flat but using the sun light through a screen.
Reply With Quote
  #14  
Old 17-06-2008, 10:30 AM
rsbfoto's Avatar
rsbfoto
Registered User

rsbfoto is offline
 
Join Date: Dec 2006
Location: Mexico City
Posts: 106
Quote:
Originally Posted by Merlin66 View Post
rbsfoto,
There's no filter to remove when viewing the Sun in Ha... it's part of the optical system; not like DSO stuf.

I agree if it's only the dust bunnies, but what about the flat field? There's possibly some vignetting in the system, this will not be corrected??
I was under the impression that all flats should be taken with the camera/ optical system which will take the lights??
Someone suggested rotating the camera and doing a median average????
Hi Merlin66,

I did not read enough and did not see you have a PST. So I guess the only way to make some flats is to cover the scope with a piece of paper when shooting the sun in order that you do not get any detail but your dust bunnies are iluminted enough to be part of the image.

Sorry first answer was stupid fomr my side
Reply With Quote
  #15  
Old 17-06-2008, 02:50 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
Solar flats

rbsfoto,
That's OK mate, happens to us all.
Not sure there will be enough light to do flats that way.... one way to find out and that's to try it.
If I get ANY sunshine today, I'll give it a go a report back.
Reply With Quote
  #16  
Old 17-06-2008, 04:24 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
Ha Solar flats

The idea of a white card/ sheet etc infront of the PST doesn't work.
There's not enough light in Ha to image!!
I think I'll have to try a different tack and do flats with the camera alone until I can solve the Ha optical system issues.
Thanks for all the input.
Reply With Quote
  #17  
Old 17-06-2008, 04:35 PM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
I'm just wondering if using something like a diffusion filter if instead of averaging the images as Registax does you convert the avi to bmps and then add all the images. There may be Ha getting though but it might not be enough to be seen with the naked eye. Have you tried taking a "filtered" Ha short and a normal dark and tried measuring the pixel value and see if there is any difference?
Reply With Quote
  #18  
Old 25-06-2008, 09:08 PM
Merlin66's Avatar
Merlin66 (Ken)
Spectroscopy Wizard

Merlin66 is offline
 
Join Date: Oct 2005
Location: St Leonards, Vic
Posts: 7,040
Ha solar flats!!!

Tried with a thin white cloth to obtain a "flat" with the PST.....
Well,
the Dark I took with the DMK shows a very tight peak on the histogram at Mean 7/ Median 7
when I gave an exposure of a couple of seconds with the white cloth I got a Mean 20/ Median 20 with a narrow distribution about 3 units wide. When I tried to expand the image... just a grey screen; no dust bunnies, nuthin!!
The best results have been a traditional flat exposure with the DMK and use this to at least remove the dust bunnies..
Reply With Quote
  #19  
Old 28-06-2008, 01:21 PM
vash's Avatar
vash (Ashley)
Registered User

vash is offline
 
Join Date: Nov 2005
Location: Gold Coast
Posts: 420
Ok, I really need to clean my 350D I guess that Isopropyl and lint free swab would be safe to use right?

I went looking at a few pharmacy's and the only place that has it only has it at 99.5% which I gather is fine, but does it matter if it hasn't got the ether in it?

I will get myself one of those arctic butterflies, but I seem to have a smudge
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 07:48 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
OzScopes Authorised Dealer
Advertisement
Celestron Australia
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
Bintel
Advertisement
SkyWatcher Australia
Advertisement
Meade Australia
Advertisement
Astronomy and Electronics Centre
Advertisement