|
sunrutas
super member
Reged: 03/04/08
Posts: 158
Loc: Visby, Sweden
|
|
Hi!
Last time I photographed the moon, I noticed something that looked like specks of dust on my computer screen, while focusing.
By rotating the camera in the focuser, I found out that it was the ccd chip that showed these spots. So I took some testshots in daylight and found lots of "artifacts" on the processed pictures. The funny thing is that I canīt find any dirt on the ccd chip.
One more thing that I found, is that the IR/UV filter attached on the end of the nosepiece is creating really nasty vignetting. I guess that it is created by the long distance between the chip and the end of the nosepiece.
Has anyone else experienced this phenomenom?
I was thinking of putting an internal filter in the nosepiece, closer to the ccd chip, but I haveīnt found a filter for internal use.
So, all you other DBK.21 users, what IR/UV cut off filter and filter "setup" are you using and with what results?
I use a Teleskop -service IR/UV block, probably made by GSO.
I saw that there are more expensive brands, Baader, Astronomik, etc.. Is it wise to go for one of these brands instead of the "low budget" T-S filter or will it be no greater quality difference with a more expensive filter?
Thanks in advance, Roger.
--------------------
My personal links:
"Astrogotland", my homepage
My CN photo gallery
|
Sunspot
Pooh-Bah
Reged: 03/15/05
Posts: 1311
|
|
I use the Baader, have since 2003 and like it a lot.
Paul
--------------------
Paul Maxson
Mewlon 250, Orion EON120, SKYnyx 2-0M, LS100F.
http://www.sunspot51.com
|
DaemonGPF
Post Laureate
Reged: 03/22/08
Posts: 3580
Loc: New Mexico
|
|
There is a definite difference between various IR/UV filters. I haven't used enough of them to tell you what is best, but I do know out of the three I used, I notice a distinct difference in my images.
--------------------
-Josh
http://cleardarksky.com/c/AlbuqNMkey.html
My AP Gallery
|
sunrutas
super member
Reged: 03/04/08
Posts: 158
Loc: Visby, Sweden
|
|
Hi!
Well, it looks as the budget -filter has to go!
I think that I will go for either the Baader, or one of the Astronomik filters.
-Any one who has experienced vignetting when using a screw on filter, with the DBK?
I thought of making the nose piece slightly shorter on the DBK in order to bring the filter as close to the chip as possible to get rid of the vignetting. -But then the nose peice will get less guidance in the holder....
Iīll try with replacing the filter, first of all!
Cheers/Roger.
--------------------
My personal links:
"Astrogotland", my homepage
My CN photo gallery
|
brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2119
Loc: 55.215N 6.554W
|
|
Quote:
Any one who has experienced vignetting when using a screw on filter, with the DBK?
Sounds very improbable to me ... unless you're working at in insanely short focal ratio, which presumably you aren't if you're imaging sun, moon or planets!
|
sunrutas
super member
Reged: 03/04/08
Posts: 158
Loc: Visby, Sweden
|
|
It is very probable, indeed!
I attach two pictures shot with the same refractor (WO Megrez 72) at the same conditions, the same camera settings, etc. The difference between the two picīs are that one is shot with IR/UV filter, the other one is shot without it.
This is "vignetting" caused by the IR/UV filter, its not due to that the image size is too large for the chip.
I dont know if the correct word for this phenomenon is vignetting, but it looks like that...
This is nothing that usually shows up on planetary images, but at some occasions I have had this effect on planetary images...
However, this is not the major issue... The speckles on the chip are a far worse problem!
They dont appear on planetary images, but if I shoot a pic of the moon, that is light and bright, it will appear.
I have cleaned the ccd careful with Baader "optical wonder" and their soft cloth without any improvements!
Could this be some kind of electronically generated "artifact" or simply dirt between the ccd and the protecting glass cover?
Have anyone experienced problems like this?
Cheers/Roger.
--------------------
My personal links:
"Astrogotland", my homepage
My CN photo gallery
|
sunrutas
super member
Reged: 03/04/08
Posts: 158
Loc: Visby, Sweden
|
|
This is a picture shot without the filter. Clearly no "vignetting". The 3x TV Barlow is used on this picture, also.
Edited by sunrutas (11/04/09 11:21 AM)
|
sfugardi
sage
Reged: 09/30/06
Posts: 332
Loc: CT
|
|
Roger, I also had these defects on my DMK21 before I sent it back for cleaning. I made the mistake of not ordering a clear filter at the time of the DMK purchase and I suspect dust got on the sensor. Even after cleaning, my DMK is not perfect but only a few faint defects are present. In your case, the main center of the chip is very clean so you should be fine for planets. For moon/sun shots, you can try just subtracting the flat frame in Registax to remove the defects although that large one may be a problem.
Regards,
Steve
--------------------
1986 Compustar C11
Toucam, DMK21 + IFW Wheel
ST-4/C90, Nikon D70s
|
sunrutas
super member
Reged: 03/04/08
Posts: 158
Loc: Visby, Sweden
|
|
Thanks for confirming that there are others than me, who has these problems with the Tis cameras.
From the day I unpacked the camera, the IR/UV filter has served as protection against dirt on the sensor.
So the dirt or defects or whatever it may be, have been there all the time.
I will try with mounting the IR filter directly in front of the Barlow the next time our simply "wonderful" (NOT!) weather allows a imaging session. Perhaps that will take care of the "vignetting" caused by the filter.
I have sent these picīs to the vendor who sold me the camera and he will contact Tis for advice.
Adding flats is one solution, but a nice, clean ccd sensor would be great!
Thanks for your input!
Cheers, Roger.
--------------------
My personal links:
"Astrogotland", my homepage
My CN photo gallery
|
brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2119
Loc: 55.215N 6.554W
|
|
Quote:
This is "vignetting" caused by the IR/UV filter, its not due to that the image size is too large for the chip.
I dont know if the correct word for this phenomenon is vignetting, but it looks like that...
Sure does! Beats me how it's happening....
|
James W.
sage
Reged: 05/14/07
Posts: 246
Loc: Maryland
|
|
I've had the same problem with my DBK camera showing spots in the pictures. I've done all I can to clean the chip, but I still get the spots, so I end up having to shoot around them and it prevents me from using my 2.5x barlow while shooting...
--------------------
James
Meade 12" LX200 GPS
Celestron C6-S
Stellarvue Nighthawk II
Coronado PST H-Alpha
DBK21AU04.AS
Meade LPI, Canon Rebel XTI
Meade 8" LX-5  RIP 10/05
|
brianb11213
Carpal Tunnel
Reged: 02/25/09
Posts: 2119
Loc: 55.215N 6.554W
|
|
Quote:
I've had the same problem with my DBK camera showing spots in the pictures.
Have you tried rubbing the sensor gently with a Q tip soaked in isoprpyl alcohol, then drying it carefully with the other end?
I find that the sensor surface on my camera is "sticky" in that dust isn't easy to get off, but once I get the camera clean, with a dust seal filter it stays pretty clean for long periods.
Here's an example of the sort of image I'm able to get without flat fielding.
2009 Oct 21, 0855 UT, PST CaK at prime focus, DMK41
The "fall off" is natural limb darkening....
Incidentally I use a plain glass dust seal "filter" (Astronomik brand) rather than a UV/IR blocker because a UV/IR blocker would prevent me imaging the Sun in calcium K or moon & planets with an infra red pass filter.
Edited by brianb11213 (11/05/09 05:08 AM)
|
|
7 registered and 4 anonymous users are browsing this forum.
Moderator: Charlie Hein, knuklhdastnmr
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 191
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
