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Gerry Casa Christiana

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Posts posted by Gerry Casa Christiana

  1. 22 minutes ago, ollypenrice said:

    I might add luminance or simply more RGB as a first step.

    The colour to luminance ratio which I use depends very much on the target. If we are trying to capture faint dusty or other broadband signal it's the luminance which will find it so I'l shoot lots more luminance than colour, as in this example. https://www.astrobin.com/335042/?nc=user  The luminance found the difficult tidal tail. However, this makes the processing harder because you need various techniques to stop the luminance bleaching out all the colour. If keeping the star sizes down in a nebula shot is the priority then I might shoot no luminance at all and use the RGB as a vehicle to carry OIII and Ha and give naturally coloured small stars. There's no one answer but the great thing is that the mono camera gives you the flexibility to choose your approach.

    The easiest processing comes from equal amounts of L and R and G and B.

    Olly

    I'm still on dslr and if price is no option God willing I would probably go mono there is still a temptation there to go one shot though. So even if you don't have a permanent setup you would say it's still faster? So using Ha on red and Oiii on blue and normal green for improving star colour and size? Learning a lot 

    Thanks

  2. 6 hours ago, ollypenrice said:

    I'm going to argue the other way but first let's get one thing sorted out: monochrome CCD with filters is faster than both one shot colour CCD and DSLR imaging. I did this image of the Heart nebula in only two hours and processed it quickly and simply. Each colour had 20 minutes and the H alpha had 1 hour.

    spacer.png

    This compares with the same equipment on the same target done 'properly' with well over 20 hours of data and complex processing:

    spacer.png

    I do not believe any one shot colour camera in an F5 system could match the first image in 2 hours.

    In this case the speed in the first image came from the use of the Ha filter but it can also come from the luminance filter which is at least three times faster than a colour-filtered image whether that's from OSC or RGB filters. (OSC and RGB are pretty much equivalent.)

    Personally I think that using the right tool for the job is always easier than using a multi-purpose tool or the wrong tool. I went straight into astrophotography with a mono CCD and almost no computing skills at all. It is often argued and assumed that you should go via DSLR into CCD but I don't agree with this. A number of people whom I've taught on my courses have said that they found DSLR to be a blind alley. Their words, not mine.

    The big argument against CCD was cost, which is fair enough, but there are now dedicated and cooled CMOS cameras which are far cheaper than CCD and in my view they have introduced an exciting mid-cost alternative.

    Olly

     

     

     

    Love it when people go against the flow :) I have to say it's quite convincing just a quick question if I may. With the first picture if you needed to improve on it would you increase time on rgb or spend more time on luminance or h Alpha? Is there a sound ratio to colour and luminance that you follow? 

    Thanks

    Gerry

  3. 16 hours ago, Jose DmCardoso Moura said:

    tighten by 2.5 mm allen screwdrivers?

    Did you tighten them? If not you must but only to the point where the mount doesn't wobble side to side if you try and shake it while on the tripod. It should be solid. 

  4. I can't say if it improved it but I can say it does not slip and polar alignment is fine on my setup as before. It's absolutely rock solid. The modification would in my opinion help to hold things firmer as your not holding the weight of the mount with the end of a bolt but it has a proper support. 

    It's a great mod and I wouldn't be without it. I changed mine as the bolt started to bend and I couldn't turn it by hand anymore. When I dismantled it the bolts had started to damage the mount even though it's not that old. 3 years roughly. Hope that helps.

    Kind regards 

    • Like 1
  5. 3 hours ago, Jose DmCardoso Moura said:

    Please, what was your polar alignment stability after the eq6 rail modification, does your mount keeps correct elevation in spite of being heavily loaded? Is it needed to have any other  modifications like substituting the three  lateral screws, tighten by 2.5 mm allen screwdrivers?

    If anything I think the polar alignment stability is about the same. Not sure about when heavily loaded as im using a skywatcher 150pds on mine. The three lateral screws I tightened the so there was no wobble but beyond that I have had no issues. 

  6. From my understanding the CLS CCD is ok for galaxies as well as nebulas whereas the UHC is not. I use it for galaxies and although I'm no expert and my colours are not always right I always use the CLS CCD as I have full spectrum like you a modified Canon 550d. I don't think it will affect the galaxy too much it just removes a lot of yellow which can be adjusted afterwards. 

    One of mine from earlier this year with the same filter. 

    IMG_0283.thumb.JPG.63e8105e9a5e17d9dd84f79d944e50e3.JPG

    Gerry

  7. Then the choice of camera? I was thinking about the 178mc but maybe 178mm would be good. It's to completely change the fov so I can get some smaller galaxies and maybe even some planetary nebulas. I noticed the 183 has the same sensor size of 2.4 does that mean if I crop I get the same image size? What about quality of image? 

     

  8. On 04/05/2019 at 13:00, Adam J said:

    This is one of the most common misconceptions in astro imaging, mono collects data faster than one shot color You will get a better image in three hours with the mono. In three hours you would do the following.

    Lum = 1.5 hours

    Red = 0.5 hour

    Green = 0.5 hour

    Blue = 0.5 hour

    Total = 3 hours

    So if you assume that each RGB pixel collects 1/3rd of the signal of the Luminance filter then you get the following.

    The formula for light gathered per channel is:

    (Filter transmission as a percentage of Lum) x  (number of active pixels) x (integration time in hours) = relative signal strength.

    **Remember that One Shot Colour uses a filter matrix and so for red only one in 4 pixels are active for green two in four pixels are active and for blue one in 4 pixels are active. For mono all pixels are always active.

    First For One Shot Colour:

    Red = 1/3 x 1 x 3 = 1

    Green = 1/3 x 2 x 3 = 2

    Blue = 1/3 x 1 x 3 = 1

    Total = 4

    Now for Mono:

    Lum = 1 x 4 x 1.5 = 6

    Red = 1/3 x 4 x 0.5 = 0.66

    Green = 1/3 x 4 x 0.5 = 0.66

    Blue = 1/3 x 4 x 0.5 =0.66

    Total = 8

     

    So using LRGB on mono you collect twice the number of photons as one shot colour in the same amount of time. So relatively your 3hours is now 6hours of equivalent data. Hence if you are short on time can you afford not to go mono?

    So long as you have a filter wheel you only need focus on Lum then just rotate for each filter.

    Adam

     

    Well that convinced me I think. So now I just have to save more money for filters and filter wheel. Now you say it I've heard this before and it does make perfect sense. I'll be saving for a mono now if it means saving time. Thanks for taking the time to explain that. 

  9. 15 hours ago, tomato said:

    No, it is the mono version with a filter wheel. 

    Now it makes sense why it was so good. I would love to do mono but it's a question of time but seems like a lot more time needed? I seem to have a couple of sessions when it's clear maybe 3 hours and then call it session done :) anyway very nice well done. 

  10. On 27/04/2019 at 15:29, tomato said:

    I am using an ASI 178 on an Esprit 150 to capture small galaxy targets. This is M51, 2.92 hrs integration time. The camera has been fitted with a Peltier cooler bringing the sensor temp down to 0-5 deg C. I am having some fun trying to get the colour balance right, this is a version modified by @Han Solo using PS. The camera is very sensitive and the small pixels can capture fine detail under the right conditions, but the FOV is limited with this scope.

    IMG_0957.JPG

    That is really nice. So you have the colour version. I've been thinking about this camera too especially for galaxies like the one above. 

  11. 32 minutes ago, carastro said:

    FWIW, I have a darker area in mine narrowband image in exactly the same place as yours and I wonder whether this is due to the nebulosity below the main nebula rather than a gradient.  It will respond to GE but looking at several other images on Astrobin, they all seem to have this darker area at the top.

    This is mine, 

    http://www.astrobin.com/full/319608/C/

    That’s a lovely picture! Yes I’m pretty sure something is there and as you say dark nebula matter probably. Glad to have resolved that. 

  12. 16 hours ago, Xiga said:

    I think you've done very well indeed here. Good job! 

    As Richard says, give GradientX-terminator a go. Even with flats, almost every image needs gradient reduction of some degree or another. Once you nail this bit, the rest starts to fall into place a lot easier. Find the darkest spot in the image, and try not to let it get much below ~ 20,20,20 in RGB levels. And finally, download HLVG and run it on a layer with the blend mode set to Color. This will remove any green cast the image has. 

    Ok used HVLG never downloaded that before! Very useful. 

    Here is my latest result. I think it’s much better.

    9CFC766C-3BE1-4C0E-8FB9-E2FA3A7533CA.thumb.jpeg.22ec06f06b287c8bb2698108a133b26d.jpeg

    Let me know if you see anything else :) 

    Thanks

    Gerry

     

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