Adam J

And now with some OIII 8 x 900s ISO 1600 OIII - Blue 16 x 600s ISO 800 Ha - Red Did not bother with any calibration frames. Posted in imaging section too but I like to share with my fellow 130PDS users

Here is 18x600s subs with my cooled 550D and Baader 7nm Ha filter. I really am looking for some advice on this as I am unsure if I have over processed it. I dont know if I should add more Ha or get the OIII next...The Ha is the most important layer as ill re-use it for luminescence later. problem is that I dont think that I have resolved much detail here as the seeing was not great when I collected this data. I posted this in the processing section of the imaging forum also but did not get much of a response so thought I would try my fellow 130PDS users. I have a couple of versions processed using different techniques, thoughts?

Its difficult to say....they are separated by a number of sensor generations. My experience of the 1000D was that it ended up only just slightly better following mono conversion.....my point being that if you do try and its successful then you may as well have something worth while for you efforts. On ebay you can often get cameras that are 'broken' in such a way as to not have any effect on their performance for astronomy..auto-focus for example or scratched view finder. So if your patient then you might be able to get something more up to date but still at a rock bottom price.

It was has been my first scope and I have not regretted it for a second. To my eye the whole colimation thing is a fuss about nothing, if you are at all technically minded as most of us tend to be it wont be an issue for you at all. It comes well below polar alignment and image processing in terms of difficulty in my opinion.

Weird thing is that very few people have done proper side by side comparisons.

The problem is applying a very very even coating. If you get a variable thickness you will have all sorts of distortions in the image and a horrible flat frame.

The picture I posted of the mono 1000D m45 is just a bare sensor. The first optical element that light reflected from the sensor encounters is my CLS clip filter followed by the Baader MPCCMKIII (which is fully multi-coated) then a threaded 2 inch UV/IR block filter (the CLS is not a CCD vershion). I would not say that I had any horrible reflections especially given how bright M45's stars are, reflections were comparable to RGB camera for an identical exposure. I think reflections are actually more likely to be an issue if you place an optical element very close to the sensor.....I just left the sensor bear with the wires protected by a plastic shim within the old filter mount. Others may had a different opinion but I would leave the sensor 'naked' as the process creates allot of debris and to be honest its useful to be able to clean the sensor using mirror lock up / manual sensor cleaning. You will end up with left over debris around the margins of the sensor as you cant get too close to the gold wires when cleaning the sensor after the mod. If debris shifted on the sensor and you had a clear glass element in front of it then you will almost certainly end up having to full disassemble the camera to clean the sensor. The best thing to reduce relections from the sensor is to keep the nearest glass element well away from it. Also having poked, heated, scraped and mechanically polished the surface of the sensor....do you really think it needs a glass layer to protect it? A clip filter will do the job of keeping dust out just fine and will be significantly further away from the sensor. You can get clear MC glass clip filters for EOS APS-C from modern astronomy....not so sure about a full frame cameras though. Dont try to bond anything to the surface of the sensor!

6D is an awesome sensor, but its also expensive. You will be a brave man to try that camera as your first mono mod. How much are the replacement sensors. I would be going for the ASI1600 at that price point myself. Also dont underestimate the effect of cooling....and that is much harder on most full frame cameras not least because of their weight.

That would happen with tilt.

Yes I agree, however...QE is a measure of the percentage of the incident photons converted into electrons and that includes the effective aperture of the pixel. So in terms of signal to noise per pixel although the Nikon cameras start out with a higher QE ~50% as opposed to Canon 40%. You have to also consider the smaller pixels in the newer cameras. I calculated it and the light collected per pixel in my 1000D at 35% QE is still more (per pixel) than the D5100 with its QE of 50%. However the D5100 has better noise so it gains quite a bit of performance from that. Incidentally in your link they compare the original 5D with the newer Sony sensor...not a fair comparison. The 5D had horrific QE (26%) and the 5D MK2 (31%) even in comparison to the 1000D (35%) so while the 1000D has poor QE its not so poor as the two sensors pictured in your link. I did think about the 550D (same sensor as 600D) with QE (41%). However my logic is that if the 1000D is breaking even using super pixel, (but worse when processed for full resolution) then the 550D might do a little better than breaking even and the D5100 might do better still....but even if the D5100 is seeing a performance advantage post mono mod due to its sensor construction I would not expect it to be a huge one, i.e. it might not be sufficient performance increase to make it worth the effort and the D5100 is more expensive. In terms of risk vs reward, independent of the camera / sensor a larger performance boost is obtained through cooling than via a mono mod in my experience. If you get a D5100 and have a go with it, please please post some analysis here. I would be very interested.

I use the Baader MPCC MKIII, yes it does not change the focal length. When Skywatcher made my 130pds they set the mirror right to the very rear of its possible travel. I have never used the GSO one.

Those look like a reflection, when you modified the 600D did you remove both of the filters or just the rear filter? You look to have a little purple haloing too. Custom white balance is what i do. I would be surprised if its coma or tilt though as your stars are still nicely round at the edges of the image.

Yes that is a good method. You can do all of this during the day if you move the polar scope horizontal and point it at a distant object. Its easier than mucking about in the dark.

Yes its tricky. If you place polaris onto the center cross and then rotate the RA axis until it moves to about the maximum distance from the center cross then adjust the reticle so that the star moves back 50% of the way towards the center cross. If you mean that the large circle around the center cross is not round then yes thats not normal. You may have taken the adjustment grub out too far and the reticle may have slipped.

Do you know how to correctly adjust and calibrate the polar scope reticle?

Ah still not got the guiding working then. Nice one removing the IR filter yourself its easy and too many people scared to do it.

What exposures did you use? Is the camera modified?

Cooled mono 1000D M45. All in all i think that the camera breaks out about even following the mod. Still it was an interesting project

Finally fixed my extra diffraction spike issue! I have confirmed the cause as focuser tube ingress into the light path. So for future reference both this and twisted spider vanes can cause the problem. The fix was to move the primary up the tube hence moving the focus out. I got some more data on M45 in the process using my mono 1000D and combined it with my original RGB as a luminescence channel. Although I had a processing misshap with the stars on the right of the image.

Its quite hard to focus a narrow band filter on a DSLR, especially as I was trying to do it fast. But I went back and forth between the two cameras multiple times ill see if any of the other mono / rgb pairs have better focus.

Here it is your way.

Ok manage to get some comparison shots of the pelican nebula. Seeing was not the best last night with lots of moisture about. 1 x 300 second ISO 800 H-A frame with the RGB 1000D and one frame with the Mono 1000D. Why only a single frame? Because I wanted to take each image as close to the other as possible to mitigate against changing conditions. For this reason I am also not cooling as it would take too long to transfare the camera in and out of the cooler and achieve the desired temperature. Mono camera 13c, RGB camera 12c. So about 10 mins between the images being taken. I have processed these in Photoshop, DSS and IRIS. Only the levels have been manipulated in each case with a slight curve adjustment with the aim of getting the best image possible out of the data. No noise reduction of other techniques. The RGB image is Red channel only converted to 16 bit gray. The red channel level in the RGB image was a long way above the Mono camera with the histogram of the mono being fully to the left and within the read noise still. Image 1: Full resolution Mono Image cropped and converted from CR2 to fits using IRIS then run through DSS without debrayering. Image 2: RGB camera image, run through DSS using bi-linear debrayering. Subsequently having Blue and Green channels removed in Photoshop. Image 3: Mono CR2 file run through DSS as super pixel debayering. Image 4: RGB super pixel debayering in DSS, Blue and Green channels removed in Photoshop. Problem is that with the cooling the noise drops massively....I am not sure which camera that will help more. I actually suspect that cooling will have a greater effect on the RGB camera due to the higher signal level in the red pixels. So I have an opinion based on this data, am interested to see what other people think though before I reveal it. Image 5: A previous picture taken with the RGB 1000D cooled to -5c. 4 x 600s exposures using a CLS filter.

Yes, given 12 months as a minimum ill be joining you, but most likely with something along the lines of the QHY163m, if nothing else the competition is likely to lower cold moss prices across the board over the next year. But until then I have what I have.

I would strongly recommend you by a cheap busted camera off e-bay and practice on it first. Broken DSLR's can be picked up for less than 30 pounds.

I dont think anyone is going to argue that the ZWO ASI1600MM-Cool is not a superior sensor for astro work across the board and by quite a long way. I have personally only spent about 50 pounds doing this as I got a broken 1000D for 40 pounds fixed it and purchased some polish on top of that. I simply cant spend over 1000 pounds on an astro camera. If this mod is not going to give me better performance I will just stick my 450D into the cool box and use that without mono modding it. it actually takes a pretty decent image at -15c. I would not recommend anyone paying for a conversion as that would not be cost effective in comparison to a dedicated camera like the ASI, for the same reason I would not recommend that someone try to convert one of the more expensive DSLR's. But if you have the skill and a lack of cash then it might help is certain areas if you convert a budget DSLR. If only for lum for galaxies or reflection nebula. To be honest its also been fun doing it. This mod really is for someone who cant afford cameras like the ASI not for someone trying to equal their performance for less cash because they are going to be disappointed.