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  #21  
Old 11-07-2013, 01:05 PM
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that will be great Rowland.
I'm buying a 1000d and am hoping to get it modded by this weekend.

a spare filter would be perfect.

I'm also buying a few spare Sony sensors used in the QHY8 and QHY8L.
I will mod these and try and swap it on my QHY8L if i'm confident enough.
we'll see how that goes.

I've been thinking of heating the sensor as well when using a cold finger.

Cheers
Alistair

Last edited by alistairsam; 11-07-2013 at 02:33 PM.
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  #22  
Old 11-07-2013, 01:12 PM
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Rowland,
Could you explain further your comment:
......leave the AA out altogether as it softens focus

The AA filter element is basically a UV -IR blocking filter....I have the spectroscope transmission curves available...this should not affect focus..
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  #23  
Old 13-07-2013, 01:19 AM
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Quote:
owland,
Could you explain further your comment:
......leave the AA out altogether as it softens focus

The AA filter element is basically a UV -IR blocking filter....I have the spectroscope transmission curves available...this should not affect focus..
Hi Ken. Several enthusiasts have been removing AA filters, by which I mean the outer glass of the sensor assembly. Apparently, one effect of the AA filter is to reduce Moire an artifact of the standard Bayer matrix and in so doing produces a slightly softer image than possible without the filter in place. This is documented on various photographic sites. The properties of UV-IR are not in dispute, it's the by-product of Moire reduction that affects image sharpness - so sharpness, not focus, is what I mean.

I was skeptical too, but a bit of research turned up a few articles on the subject.

Alistair, I also have a couple of custom made cold fingers for a 1000D - ? One needs a bit of work the other is a bit short.
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  #24  
Old 13-07-2013, 10:12 AM
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Rowland/Alistair,
Whoooo
You've opened one hellava box with that AA filter comment!!!

I did the usual on-line search and I'm amazed that the issue of Moire fringes/ anti-aliasing hasn't come up before in the amateur astronomical community!
Sure, we all talk about the loss of resoution due to the Bayer matrix, but few (if any) take note that the inbuilt "AntiAlias" filter element actually blurs the image - on purpose, to prevent (or reduce) the Moire effects...

What does this mean to our "highly detailed DSLR images" or in my case the definition of fine absorption lines in DSLR spectral images.....
Hmmmmm
Need to spend a but more time and research on this one.
Thanks for raising it to the consciousness level.

Last edited by Merlin66; 13-07-2013 at 10:44 AM.
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  #25  
Old 13-07-2013, 10:41 AM
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Hi Ken,

I did read about the AA filter and moire a bit but didn't pay much attention until Rowland pointed it out.
So in short, its better to take it out and replace it with a normal UV/IR filter?
in the pre-press industry, we normally do use a blur filter to remove moire from scans of printed material. kind of the same thing I think.

yes I'll PM you about the cold fingers. i've got a few ideas on preventing frosting but i'll finish the b&W and IR filter mod and now the AA filter mod first and do some narrowband now that the moon is out for the next 2 weeks or so. will then move on to the cooling.

I finally managed to install the 350d drivers in windows xp and i'm figuring out how to take exposures longer than 30secs. if that works, i'll give it a crack on the first clear night out here.
i'll see if I can get a few 5 min exposures with an LP filter with the mono 350D and a few RGB exposures with the QHY8L and overlay the two.

I'm wondering if there is any interest out there for photographers to use a B&W DSLR.

Cheers
Alistair
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  #26  
Old 13-07-2013, 10:46 AM
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It certainly appears that removing the AA filter (doesn't have to be replaced - in normal mods) or replacing with a UV-IR cut for non spectroscopic work would be a way to go.
I need to find some astronomical/ spectroscopic examples of Moire fringing/ antAlias effects before I start to panic.
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  #27  
Old 13-07-2013, 12:25 PM
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Ken. An example is the image sharpness of my FujiFilm X-Pro1. The colour matrix is non-standard and designed to avoid Moire. Consequently, the AA filter is very weak, if not non existent, hence, image sharpness. Having said that Moire is noticeable from time-to-time. Almost inescapable.

One Mark IIID owner removed the AA filter shortly after purchasing the camera, with noticeably better image sharpness - but, Moire is problematic because of the standard Bayer matrix minus AA.

I was very disappointed with my first mod, because the image was too soft. The second is much better without the AA filter.

As an aside. Removing the AA/Piezo assembly provides a niche for a small nichrome dew heater on the plastic filter frame. A very thin heater element will fit nicely into the depression that houses the Piezo unit. DSLR cold finger cooling needs a solution to sensor fogging. With that, it will be very successful.
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  #28  
Old 13-07-2013, 02:23 PM
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Great thread. I've got a little Nikon D40 lying around. From this related US thread, the Nikons appear easier to modify.

http://www.cloudynights.com/ubbthrea...fpart/all/vc/1

Anyone in Oz got the skills?
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  #29  
Old 14-07-2013, 02:28 AM
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Hi Logan,

if I'm able to acquire spare sensors, I could mod the sensor and just swap the sensor from cameras. should be simple enough and least risk.
something like this
http://www.ebay.com.au/itm/GENUINE-N...061eb09&_uhb=1

I've got the B&W modded 350D drivers working in XP now, I need to make that serial cable for bulb exposures, and hopefully we have clear skies on monday and tuesday, i'll try out some Ha and luminosity frames and post results here.

by next week I should have a full spectrum modded true mono 1000D, I'll remove both the AA and IR filters. anyone know where I can get clear glass cut to dimension in melb?

Can't wait cause its so much easier to use via USB than the older ones like the 350D.

I will then have to pick Rowlands brain on cooling it.


Cheers
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  #30  
Old 14-07-2013, 08:57 AM
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Alistair,
You may widh to consider as an "interim" just using a microscope slide glass...these are nominally 1.0mm thick and come 25 x 75mm -easy to cut. If you want to come over to Maribyrnong you can pick up a couple...
(I use them as a beamsplitter plate in the spectroscope)
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  #31  
Old 14-07-2013, 08:54 PM
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Quote:
Originally Posted by alistairsam View Post
Thanks Ken, Bojan, Rowland,

the guys in SGL have gone through several chemicals and some of the partially successful methods were
using a buffing tool with a dremel - worked for a 1000D
some sort of a paint remover
toothpaste!!

but after thinking about it and the fact that the photosites are composed of multiple layers sandwiched and are quite hard, i thought the wooden tool was the safest because it doesn't cause any scratches on the layer beneath the CFA and also because the CFA layer is brittle.

one of the members there, Gina, did every imaginable thing possible to remove the glass off a 1100D sensor and finally gave up. these sensors are actually a lot tougher than people think.

and as Ken mentioned, removing the IR filter and removing the CFA gives you a full spectrum camera, only limited by the slight loss in sensitivity due to the microlenses being removed which is unavoidable, and the fact that the QE of these sensors are lower than astro CCD's.

but still, making use of all 4 pixels opens opportunities for so many applications, narrowband, Ha, luminance, all at a fraction of the cost of a similar sized CCD.

I can now do narrowband imaging from my light polluted backyard. once I cool it of course which is another challenge on its own.

I figured, if I'm going to spend 2.5K toward a CCD, I might as well spend a few hundred trying it with DSLR's and worst case, each 350D sensor is $60 on ebay. so its very cost effective and is not really that hard if you're good with small things.

it certainly requires a steady hand and I'm used to soldering SMD's by hand, so I had no issues controlling or restricting my movement.

Bojan, it takes a bit of practise to control the hand movement based on the microscope visual feed, but its quite easy.
as I mentioned, the two edges with the contact wires are the most risky cause one contact on those wires and its very likely the sensor would be dead.

I'm thinking of moving on to a 400D or a 1000D which I know is noisier but is quite cheap and the glass does come off.

Bojan, you're welcome to come over. but be prepared to spend atleast a few hours. I have heaps of questions for you as well. pls drop me a PM.

Cheers
Alistair
I'm the nutter that started that thread on SGL and buffed down the 1000d sensor to see what would happen

It took a Kiwi to kick it off haha
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  #32  
Old 14-07-2013, 09:14 PM
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Quote:
Originally Posted by Rac View Post
I'm the nutter that started that thread on SGL and buffed down the 1000d sensor to see what would happen

It took a Kiwi to kick it off haha
hey Ray

Edit: sorry just checked and noticed it wasn't Gina, got a bit confused. but that thread was very inspiring, thanks. what made you think of it?
for me, it struck me at church, I clearly wasn't paying attention, but I was so excited I had to come out and google it and found your thread.

did you try any astro imaging with the 1000D at all?

I tried 30s darks with the 350D and its quite noisy. so for decent narrowband work, these will need to be cooled unless the subs can be less than 5 mins. not sure how much signal will be present.

cheers
Alistair

Last edited by alistairsam; 14-07-2013 at 10:14 PM.
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  #33  
Old 15-07-2013, 05:32 AM
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I don't know when I thought of it but it would have been to save money somehow, I think of lots of things but most of them don't work lol.

I only did some test shots. There was an increase in sensitivity but it wasn't huge. That wouldn't matter though as it would be a huge gain for narrow band work.
Yes cooling is very important with a dslr.
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  #34  
Old 15-07-2013, 05:33 AM
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If we can come up with a practical sensor face heating solution the rest is easy.
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  #35  
Old 15-07-2013, 09:28 AM
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Quote:
Originally Posted by alistairsam View Post
Hi Logan,

if I'm able to acquire spare sensors, I could mod the sensor and just swap the sensor from cameras. should be simple enough and least risk.
something like this
http://www.ebay.com.au/itm/GENUINE-N...061eb09&_uhb=1

I've got the B&W modded 350D drivers working in XP now, I need to make that serial cable for bulb exposures, and hopefully we have clear skies on monday and tuesday, i'll try out some Ha and luminosity frames and post results here.

by next week I should have a full spectrum modded true mono 1000D, I'll remove both the AA and IR filters. anyone know where I can get clear glass cut to dimension in melb?

Can't wait cause its so much easier to use via USB than the older ones like the 350D.

I will then have to pick Rowlands brain on cooling it.

Cheers

Alistair, thanks for the kind offer. I'm new to this mod and still considering he pros n cons. Cheers.
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  #36  
Old 15-07-2013, 01:20 PM
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This is what I have in mind for sensor dew protection.
Attached Thumbnails
Click for full-size image (DSLR Sensor filter glass de heating.jpg)
143.9 KB173 views

Last edited by rcheshire; 15-07-2013 at 05:14 PM.
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  #37  
Old 15-07-2013, 03:16 PM
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Hi Rowland
I presume you meant to attach something?
What if we use an in body filter like this one to create an air tight chamber in front of the sensor similar to ccd's.
http://www.sciencecenter.net/hutech/filters/ffilter.htm
But if heating the glass face is the only option we could use smd resistors on the glass face to heat as they would provide higher resistance than nichrome wire for the space that's available.
Or if we replace the aa filter with clear glass and create an air tight space in front
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  #38  
Old 15-07-2013, 05:28 PM
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I did intend attaching something - now attached.

It is easy enough to ensure that the air between the sensor and glass is dry by leaving the assembly in a sealable plastic bag with dessicant for a while and then sealing with silicon. That worked perfectly for my 1000D cooling mod. The problem is keeping the outside face free of condensation.

I'm looking at a heat source that will fit into the very tight space between the shutter and sensor face. Nichrome is thin enough. SBIG do the same with their ST-8300, installing a small strip heater adjacent to the outside glass.

This should provide a localised warm region around the face of the filter - that's the theory? Open to suggestions.
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  #39  
Old 15-07-2013, 06:08 PM
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hi rowland,

can't you keep the outside face free of condensation by adding an LP filter at the end of the T adaptor or nosepiece?

when I had the same issue with my QHY8 nosepiece, adding a coma corrector with a spacer in a dry bag kept condensation away and I didn't need a heater strap on the spacer as is normally done.

other option for a dslr would be an eos clip filter.
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  #40  
Old 15-07-2013, 06:37 PM
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I think that works for sealed set ups, such as cooler boxes. Cameras are leaky, otherwise. I do not intend sealing the camera, so a different approach is needed.
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