From: Mark Gaffney <markgaffney@me.com>
Date: February 12, 2010 6:17:23 PM MST
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Scorpion Sun Images...
Hi Ray,
Oh I see! (I was thinking of a cloth or something when you mentioned linen..) I`ve just blown off the cameras with the big air compressor in the shed.(see the message to Alan). I couldn`t see anything at all with the inverted eyepiece except the outside rim but maybe I can test with a desk lamp after lunch. I might be able to see if the blowing has done any good?
Mark.
On 13/02/2010, at 11:58 AM, Ray Byrne wrote:
Mark,
The linen tester is the photo on the page that I gave the link to. It is a magnifying glass that enables printers and designers to look closely at the dot structure of printed material.
Here it is:
<linen-tester.jpg>
You need to put your camera under a lamp like one has on a desk and shine it right into the camera. Then look obliquely so as not to get into the way of the light from the lamp and focus the magnfyer into it to see the window above the chip clearly. A linen tester is easy to use for this and has just the right magnification a magnifying glass may be too low in magnification that is why I mentioned the trick with eyepieces. You will not be able to use you camera effectively on most extended objects (the Sun, Moon) or even the planets with all that gunk on it as your images will have donut shaped artifacts all over them. Basically in micro terms they are filthy (sounds harsh but true sorry mate). I'll see if I can track down a supplier in blighty that will ship Opti-Clean to Aus. I work with a few astro suppliers doing their mag ads and they will sort something out I'm sure.
ATB
Ray
On 12 Feb 2010, at 23:58, Mark Gaffney wrote:
Hi Ray,
I`ve been to your website (very impressive!) but couldn`t find the linen tester..? I also had a quick look backwards through my 25mm eyepiece at the glass over the chip of the Scorpion but think the magnifying glass might be a better shot-(if we could find it!) I probably need better light to be able to see anything...will take it inside soon where there`s light coming into the dining room from a big window. Looking at it of course dosen`t clean the glass & held up a certain way to a flourescent light last night (through nosepiece & Baader UV/IR cut filter-which is what Alan`s advising I use immediately..) the camera was still showing some small marks. I know they`re there anyway!
Mark.
On 13/02/2010, at 2:41 AM, Ray Byrne wrote:
Hi Mark,
Adding to my last mail. After emailing you I remembered I had a dust mote on my DMK and thought of doing the Opti-Clean thing on it. Firstly I took my linen tester (printer's magnifying glass) and took a look and I could see the offender sitting on the glass window in front of the CCD chip. I took a small sable hair brush and gently flicked it off so no need to use Opti-Clean. Take a look at your camera with a strongish magnifying glass an eyepiece turned around the wrong way works but use something around 25mm or longer as it will be too powerful and you'll have trouble seeing anything and the depth of field is very narrow.
Look at this page on my company website it has a linen tester on it <http://www.raycreative.co.uk/raycreativeconta.html>
IHTH
Ray
On 12 Feb 2010, at 11:55, Mark Gaffney wrote:
Hi Ray,
This seems the best listing for Opticlean with shipping to Australia. This is a spray though & slightly different to the type in the Cloudy Nights Review. I can just about afford this product next pay. What do you think?
Mark.
On 11/02/2010, at 10:01 PM, Ray Byrne wrote:
Hi Mark,
Just a couple of things that may help firstly I use a product called Opti-Clean which is a thick liquid that you let flow off the supplied brush on to the glass surface and let dry to form a skin. One then uses the supplied sticky tabs to peel off this skin which also remove any gunk that's on the glass surface. It really does work very well and leaves no residue here's a link for you <http://www.cloudynights.com/item.php?item_id=551>
As regard focusing - once you find a good focus with your camera take a spare eyepiece of medium power for your C.925 say a 12mm, remove the camera and insert the 12mm (or whatever) into the EP holder and without touching the focusing knob slide the 12mm EP in the holder until it's also in focus. Use a marker pen and mark a line (or if you not precious about it score the barrel) where the EP meets the top of the holder. Next time you can put this EP in focus visually then when you insert your camera it will be in focus or very close to.
IHTH
Ray
On 11 Feb 2010, at 04:12, Mark Gaffney wrote:
Hi Alan, Good suggestions! I had on my list some cleaning alcohol as now I think about it the watermarks are the result of cleaning with some detergent in water. Do you mean using a size say of 800 x 600 pixels with this camera? Full size is rather too large practially with my 12" iBook. I"d love some form of automated focuser- but that"s not immediately possible. As to getting the right exposure I had the base exposure rate set at it"s lowest setting 16.67ms & got my best result eventually at 30 fps. I used both the incremental adjustment 10 ms at a time & also the slider setting it as close to what seemed right given the range available ( all the time jogging from the scope to where I could see the screen to get some sort of marriage between focus & exposure!) This was a very fine distinction given rather extreme conditions. Focusing is one thing obviously improveable & exposure seemed to be reliant on the former for any greater precision? Beyond trying without ROI what suggestions would you have? Focus & exposure both seemed to me just very tiny nudges before things were either in whack or out! Brightness is of course the other variable & I found a setting of about 400 was right for this morning"s conditions. I guess this is what"s left of the large sunspot 1043 after several rainy mornings here! Might the Sun be brighter or more intense here in Australia too...?
Mark.
Sent from my iPod
On 11/02/2010, at 2:28 PM, Alan Friedman <alan@greatarrow.com> wrote:
Hi Mark,
A couple of suggestions:
1. Get an observing cloth. I use a piece of black polar fleece with a silver fabric sewn to one side to reflect the heat. It covers my head when I am doing visual observing, and my head and laptop when I am capturing solar data with Astro IIDC. When selecting a piece of cloth, choose something supple and hold it up to a light bulb to make sure it isn't too sheer.
2. Your focus is off - I can tell that by the fact that your dust motes are as close to focus as the sunspots. Dust motes are always a problem with these sensors. You should have a can of compressed air for photographic use. You can use it to blow dust off your optics and off the chip of your camera too. Just be careful not to shake the can and point and release some air at your hand right before cleaning to be sure that no propellant is being released.
3. Get the exposure right. Use the histogram in AstroIIDC to ensure that you are not cutting off data at the white end. Your image is mostly blown out in the whites. When properly exposed, the solar disk should have tone throughout - no white. You can adjust the levels afterward if needed, but you cannot put back what was not recorded in the first place - in the case, the detail in the brightest sections of your image.
4. You really want to master the technique of finding the sun by minimizing the shadow. There are also some finder scopes made by Televue and others that work from a cast shadow. You don't want to be sighting towards the sun to locate it in the scope. A couple of quick glances and you'll have lots of nice spots in your eyes that take time to go away before you can see the laptop screen again.
5. Don't use ROI... there is no advantage for you. You don't need to average many if any frames when imaging the sun - you can shoot it with 0 gain (brightness) so the individual frames will have lovely signal and very little noise. Most of my recent solar images are constructed using single movie frames without any stacking at all.
practice... practice - it's summer!
best,
Alan
On Feb 10, 2010, at 8:10 PM, Mark Gaffney wrote:
You guys have been busy whilst I`ve been doing this! These Suns are
shot with a Scorpion 20SO mono camera using Baader solar film & my
C9.25 scope at prime focus. The camera is set to 814 x 618 pixels
ROI...I think for the 2nd of these I went to 30 fps, the first one was
at 15 fps & using very minimal exposures .90 ms for both, I think. I
have to put my lap-top over a bit under a bush & a good few feet from
the scope or I can`t see anything because of glare ( we don`t have a
useable beach umbrella at present..) so focusing is very difficult
(not to mention co-inciding this with getting an acceptable exposure.
(thank goodness there were no march flies this time..! -I had some
Aeroguard & there were less around-also I remembered to wear a hat but
it was still very hot especially by the time I was ready to give
up! ). I found a useful expedient was to put a small corner of the
solar film (about 1 inchr or more intense here in Australia too...?
Mark.
Sent from my iPod
On 11/02/2010, at 2:28 PM, Alan Friedman <alan@greatarrow.com> wrote:
Hi Mark,
A couple of suggestions:
ages before this trying to simultaneously locate & focus the Sun-using
smallest shadow etc.... I don`t know how I`m getting these blotches on
the glass cover of the chip..the camera is covered except when I take
the grey PGR cover off to test something? I certainly don`t have time
when all set up at the scope to be cleaning cameras, especially with
the Sun which has a limited time it can be imaged because of the heat!
But it`s probably spoiled these images for what they`re worth. Lastly,
I`m finding a single sharpest frame seems to be the best option for
clarity...& I`m only posting them as small size attachments here.....
Mark