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Field Flattener

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#1 Hook

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Posted 24 July 2021 - 06:51 AM

Hi all.

 

I need a field flattener. Seeking advice.

 

I have a canon 1300d on a skywatcher startravel 120.

 

Would like to keep to around a 200 budget if possible, thanks



#2 asanmax

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Posted 24 July 2021 - 10:48 AM

I'm afraid Startravel 120 is not suitable for astrophotography. You'll see too much of chromatic aberration.

If you do decide to try it anyway, you may want to buy a budget flattener such as a Starfield.



#3 spazmore

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Posted 24 July 2021 - 11:25 AM

With my Celestron C150R refractor (750mm f/5), I have used an Astro-Tech AT2FF and the HoTech SCA to clean up the edges on an APS-C sensor; they both seem to work mostly the same in any of the scopes that I've tried them in. For reduction and flattening, the Orion 0.8x seems to do a decent job, but your chromatic aberration will increase significantly.

 

As asanmax mentions, you're going to get a ton of chromatic aberration. I started astrophotography with the f/5 achromat; I have since "graduated" to newts and the AT60ED.



#4 KLWalsh

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Posted 24 July 2021 - 03:20 PM

Look for a broadband green filter, one that will trim away most the deep reds and blue and thus reduce a lot of the chromatic aberration, then shoot monochrome. Or maybe think about narrowband, like H alpha. You’ll still need a flattener.
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#5 Hook

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Posted 25 July 2021 - 06:21 AM

I'm afraid Startravel 120 is not suitable for astrophotography. You'll see too much of chromatic aberration.

If you do decide to try it anyway, you may want to buy a budget flattener such as a Starfield.

Well I compared 1 of my 30 sec shots to a photo that had been stacked and processed by a pro. I saw no difference in CA, and I zoomed right up to my stars.

CA worsens in light polluted areas and becomes less from dark skies. I guess because my area is dark skies the CA is far less than if you were in downtown Manhattan.

 

So I tested photos taken last night at various ISO and exposure length.

Photos at 200 ISO exp 3 mins gave slight CA on the brightest stars, (7). I am sure I could process that in any photo software.

Same photo at ISO 200 with 5 min exp yielded same result.

Same photo at ISO 400 exp 5 mins yielded same result

Same photo at ISO 400 exp 3 mins gave practically no CA

Same photo at ISO 800 exp 30 sec gave no CA

 

We are not all looking to get our photo's into "NASA weekly".

 

Not a very helpful post.



#6 17.5Dob

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Posted 25 July 2021 - 02:32 PM

CA worsens in light polluted areas and becomes less from dark skies. I guess because my area is dark skies the CA is far less than if you were in downtown Manhattan.

LP has no effect on the inherent quality of your optics......a f5 achromat will always show a lot of CA.

I use a Hotech SCA flattener with my APO's. It gives pinpoint stars corner to corner  on an APS-c sensor.


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#7 galacticinsomnia

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Posted 25 July 2021 - 07:08 PM

I'm using the Orion FF and FF/FR, though it is not advertised as a FF, it just delivers those optical qualities.  Orion 8893 and 8894 respectively.

You will need to play with backspacing for any FF/FR to determine the best image quality for your scope.  As above, the Hotech is a great piece of kit, but I couldn't get the kind of sharpness I expected and it went back, though I have to say, I didn't put it through all of the variations with backfocusing that I do now, so it may work perfect for you.

I can say however, I'm a fan of the Orions so far for the money and very quick 3 or 4 day delivery straight from Orion.  If you order through amazon, you have 30 days to give it a shot and if you don't like it, send it back.

Works pretty great on my RC6 too.

Clear Skies !!



#8 17.5Dob

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Posted 26 July 2021 - 02:39 PM

I'm using the Orion FF and FF/FR, though it is not advertised as a FF, it just delivers those optical qualities.  Orion 8893 and 8894 respectively, I'm a fan of the Orions so far for the money and very quick 3 or 4 day delivery straight from Orion.  If you order through amazon, you have 30 days to give it a shot and if you don't like it, send it back.

Works pretty great on my RC6 too.

Clear Skies !!

My Orion FF was total junk and exhibited horrendous Newton rings, that's why I got the Hotech.

49632539133_9ec9150188_o.jpg


Edited by 17.5Dob, 26 July 2021 - 02:40 PM.

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#9 galacticinsomnia

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Posted 26 July 2021 - 04:53 PM

My Orion FF was total junk and exhibited horrendous Newton rings, that's why I got the Hotech.

49632539133_9ec9150188_o.jpg

That is really bad :( 
The hotech was a nice piece of kit, but I was being quite ignorant when it came to backspacing and really had no idea there could be a 50mm difference depending on scope.
Kinda wish I kept it, but was able to get the two orion ones for almost the same price, and so far, they are doing pretty well. 

Clear Skies !!



#10 Hook

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Posted 27 July 2021 - 05:05 AM

For a telescope not suitable for atp, no field flattener, first attempt, no experience in post-processing........I think I have done a good job.

 

whirlpool small size.jpg


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#11 vidrazor

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Posted 27 July 2021 - 03:04 PM

For a telescope not suitable for atp, no field flattener, first attempt, no experience in post-processing........I think I have done a good job.

That a good start. I can see why you want the FF. How did you shoot and process it? You can probably get better core and better shadow detail tweaking your data and making some gradient masks. I processed your image posted here, and it seems you can get more from your 16/32-bit data. If that scope is all you have, just keep shooting with it, don't worry too much about distortions and aberrations. Just get a good handle on shooting and processing data.
 

Attached Thumbnails

  • m31.jpg

Edited by vidrazor, 27 July 2021 - 03:12 PM.

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#12 Hook

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Posted 27 July 2021 - 08:27 PM

That a good start. I can see why you want the FF. How did you shoot and process it? You can probably get better core and better shadow detail tweaking your data and making some gradient masks. I processed your image posted here, and it seems you can get more from your 16/32-bit data. If that scope is all you have, just keep shooting with it, don't worry too much about distortions and aberrations. Just get a good handle on shooting and processing data.
 

Thanks. Good to read from someone that understands.

 

100 lights @ 30secs, 50 darks, 30 flats, 20 bias, used DSS, then Gimp.

 

I did use many of the tools in gimp, including plug-ins. I did get the sharpness to how you did, but preferred the "sepia" look. I looked at making it more colourful, but didn't like it. I looked at images on google that others had taken, and they were vastly different to each other. I guess it boils down to each personal preference.

 

I do have an 8 inch dob also, but I am currently working on converting my shed to an observatory, so I do not have to move the gear in and out all the time. The dob is ready for the camera as I moved the mirror.

 

As you say, I will continue with this one for the moment as I am getting plenty of practice, and no....I will pay no attention to those that think anything that is not labelled as "photo ready" is no good. I have more or less decided to go for this https://www.firstlig...-flattener.html which is probably the one you are recommending? I am guessing I can use that in my dob also.

 

This telescope is easier to move around on the tripod for the "in-out" routine. I leave it all set up but will not leave it outside.

 

Just brought all my gear back in from another "shoot" tonight. I was getting the elephants trunk neb, but stellarium did not want to play ball....for whatever reason, and at one point I could not get my correct location in the sky......**** frustrating!......and then after getting 20 shots cloud rolled in. I gave it up as just another trial run. PHD2 gave me grief also, so I just relied on using stellarium and thankfully I get good tracking for 1 minute without guiding, so was taking 30 sec shots.

 

I believe the back focus on the FF is 55mm for my canon, but they are ready with that back spacing so I just use the t-ring.


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#13 vidrazor

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Posted 27 July 2021 - 09:34 PM

It was 17.5Dob who mentioned the HoTech (who dreamed up that name, LOL!), although I recently picked one of those up myself for an SVBONY 102mm f/7 I recently got. The only thing I don't like about it is that it's a 2 inch flattener with a 42mm T mount. I don't know why on earth they didn't put a 48mm thread on it. On the flip side, it seems to line up right at 55mm on my cameras. I have yet to shoot with it and the SVBONY, as weather has been crap, and my GOTO mount went back for repairs. I did have the SVBONY perfectly balanced on my SkyGuider Pro however, although it's technically not really made to handle a load like that scope, along with the camera, etc. :) It'll be rough to find a tiny target with that setup. What are you tracking and guiding with, BTW?

 

I don't think the HoTech flattener will work on the Dob. I could be wrong, but I believe Newtonians, and mirrors in general, need a different type of flattener. Perhaps 17.5Dob can chime in on what's good for Dob. If you get another refractor you can use it with that if it's between f/5-8.

 

Gimp has proven itself a good data processing resource. I would work more with it if it had adjustment layers, and frankly I'm surprised at this point in time it doesn't, so everything done in it is destructive. It does have some interesting operators and controls parameters for them. Color is definitely whatever you like. There's a group of people that feel color and processes have to be X, but really one look online at any target makes you wonder where that train of thought comes from. :)  You might also want to try running your data through Siril. It has a lot of good tools to help process data. Granted, you only have 25 minute's worth, but it's a bright target, and I've been surprised more than once from what I got out of Siril from similar total time. Like DSS, Siril is a free open source program.



#14 Hook

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Posted 28 July 2021 - 05:53 AM

It was 17.5Dob who mentioned the HoTech (who dreamed up that name, LOL!), although I recently picked one of those up myself for an SVBONY 102mm f/7 I recently got. The only thing I don't like about it is that it's a 2 inch flattener with a 42mm T mount. I don't know why on earth they didn't put a 48mm thread on it. On the flip side, it seems to line up right at 55mm on my cameras. I have yet to shoot with it and the SVBONY, as weather has been crap, and my GOTO mount went back for repairs. I did have the SVBONY perfectly balanced on my SkyGuider Pro however, although it's technically not really made to handle a load like that scope, along with the camera, etc. smile.gif It'll be rough to find a tiny target with that setup. What are you tracking and guiding with, BTW?

 

I don't think the HoTech flattener will work on the Dob. I could be wrong, but I believe Newtonians, and mirrors in general, need a different type of flattener. Perhaps 17.5Dob can chime in on what's good for Dob. If you get another refractor you can use it with that if it's between f/5-8.

 

Gimp has proven itself a good data processing resource. I would work more with it if it had adjustment layers, and frankly I'm surprised at this point in time it doesn't, so everything done in it is destructive. It does have some interesting operators and controls parameters for them. Color is definitely whatever you like. There's a group of people that feel color and processes have to be X, but really one look online at any target makes you wonder where that train of thought comes from. smile.gif  You might also want to try running your data through Siril. It has a lot of good tools to help process data. Granted, you only have 25 minute's worth, but it's a bright target, and I've been surprised more than once from what I got out of Siril from similar total time. Like DSS, Siril is a free open source program.

50 mins worth of lights.

 

I am using an eq5 with synscan goto. Recently stripped it down to grease and mesh the gears as best I could, seemed to make a difference. The night of taking the Andromeda PHD2 guided perfectly all night long without a hiccup. The unfortunate part of ATP is the cost. No matter what you have someone will say, "you need xyz". When I win the lottery I will buy "xyz". Same with the software. We have just learnt 1 thing then get told to use another, and when we learn that....another software is out with people telling us to use that one.

 

I wonder sometimes if the whole set-up is just to make us buy newer gear and buy new software, (or promote free ones). Funny how they still use PHD2 though, there seems to be no alternative to PHD2 for guiding. When I used just stellarium with my scope and Altair to capture, everything ran perfectly.....no lag/freezing.....but drifted after a time. Since using PHD2 with stellarium there is lag/freezing in both. PHD2 disconnects the camera saying it has not had a frame for over 17 secs, yet if I open altair the camera is working perfectly. In Stellarium it freezes for about 5 secs at a go...quite often, then the scope crosshair sits away from the target, even though I am on the target with my camera, and pressing "slew", or "sync" does nothing. I have a fast modern laptop more than enough to run those programs. I use a USB extension with a built-in power sender and it works fine with every capture software except PHD2. Even eqmod states, "non responsive" at times, and when I use the slew controls stellarium shows the scope going from 1 part of the sky to somewhere else at lightning speed......and I am nowhere near that spot, I have simply moved a fraction. Same with PHD2, the graph showing tracking just freezes for about 5 secs then continues. I am using an FTDI serial connector for synscan with the correct drivers. I run eqmod as admin, and then open stellarium and PHD2 as admin also. If I connect just eqmod there is no delay or "non-responsive" comments from it, it slews just fine immediately. There seems to be a problem using stellarium with it. If I run eqmod, then PHD2, that seems fine also.

Do I need to be connected to the net for them to work in unison? I am currently connected via wi-fi, but the signal is very poor. I do have a hard-wired connector which is in my PC and I can simply swap it over to the laptop.

 

Gimp has layers which do not affect other layers.



#15 Hook

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Posted 28 July 2021 - 08:10 AM

So I connected everything to my PC instead of laptop. Running a test from inside so cannot use guiding, but have camera connected and working, PHD2 open, Stellarium open, and EQMOD working. So far there are no odd movements and the system has been on a star for over an hour without drifting. I have the internet connected and disconnected and no difference. I am thinking that the laptop may not be pushing enough power out to work them all, and hence getting lag/freezing. I am going to leave it running to see what happens. I also used the movement controls on eqmod and it worked without problems.



#16 vidrazor

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Posted 28 July 2021 - 09:59 AM

50 mins worth of lights.

 

I am using an eq5 with synscan goto. Recently stripped it down to grease and mesh the gears as best I could, seemed to make a difference. The night of taking the Andromeda PHD2 guided perfectly all night long without a hiccup. The unfortunate part of ATP is the cost. No matter what you have someone will say, "you need xyz". When I win the lottery I will buy "xyz". Same with the software. We have just learnt 1 thing then get told to use another, and when we learn that....another software is out with people telling us to use that one.

 

I wonder sometimes if the whole set-up is just to make us buy newer gear and buy new software, (or promote free ones). Funny how they still use PHD2 though, there seems to be no alternative to PHD2 for guiding. When I used just stellarium with my scope and Altair to capture, everything ran perfectly.....no lag/freezing.....but drifted after a time. Since using PHD2 with stellarium there is lag/freezing in both. PHD2 disconnects the camera saying it has not had a frame for over 17 secs, yet if I open altair the camera is working perfectly. In Stellarium it freezes for about 5 secs at a go...quite often, then the scope crosshair sits away from the target, even though I am on the target with my camera, and pressing "slew", or "sync" does nothing. I have a fast modern laptop more than enough to run those programs. I use a USB extension with a built-in power sender and it works fine with every capture software except PHD2. Even eqmod states, "non responsive" at times, and when I use the slew controls stellarium shows the scope going from 1 part of the sky to somewhere else at lightning speed......and I am nowhere near that spot, I have simply moved a fraction. Same with PHD2, the graph showing tracking just freezes for about 5 secs then continues. I am using an FTDI serial connector for synscan with the correct drivers. I run eqmod as admin, and then open stellarium and PHD2 as admin also. If I connect just eqmod there is no delay or "non-responsive" comments from it, it slews just fine immediately. There seems to be a problem using stellarium with it. If I run eqmod, then PHD2, that seems fine also.

Do I need to be connected to the net for them to work in unison? I am currently connected via wi-fi, but the signal is very poor. I do have a hard-wired connector which is in my PC and I can simply swap it over to the laptop.

 

Gimp has layers which do not affect other layers.

Ooops, right, my mistake. That's still not much light, but M31 is fortunately a bright target.

 

Yeah, there's a guy named Roger Clark who gets pooh-poohed here a lot because he goes against the grain of what it considered the "proper" way to shoot and process, and his approach doesn't mandate using more and more expensive gear. ;)

 

If you haven't tried Ekos, you may want to give that a shot and see how it works for you. It's a one stop solution for astro. It's most popularly used in the Astrobbery setup on a Raspberry Pi, but any laptop running Linux will run it, If you want to test it out, simply load a Linux executable on a USB stick and boot your laptop off it and try it out to see if it works for you.
 


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#17 kel123

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Posted 28 July 2021 - 11:30 AM

I am also a fan of using or trying out what you have, instead of being "bamboozled" into spending more money but there is also nothing wrong in someone pointing out that an achromat has chromatic aberration in case you didn't know. You were obviously prepared for such comment but it is pure science. And light pollution has nothing to do with it.

No one should tell you what you should do and shouldn't do, only pointing out something you should know in case you don't. But overlooking something doesn't mean it doesn't exist. It shouldn't make you angry. But you are right not to care and do what suits you at this time as far as you believe that your images are good enough.

Having said that, you are really making good use of what you have and I believe you can really go far in proving naysayers wrong. People like you inspire others who are not disposed to spending a lot of money on the hobby and doing things the "acceptable" way. Sometimes, it almost seems like a competition of who has the deeper pocket. So, I feel your pain.
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#18 Hook

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Posted 28 July 2021 - 02:40 PM

I am also a fan of using or trying out what you have, instead of being "bamboozled" into spending more money but there is also nothing wrong in someone pointing out that an achromat has chromatic aberration in case you didn't know. You were obviously prepared for such comment but it is pure science. And light pollution has nothing to do with it.

No one should tell you what you should do and shouldn't do, only pointing out something you should know in case you don't. But overlooking something doesn't mean it doesn't exist. It shouldn't make you angry. But you are right not to care and do what suits you at this time as far as you believe that your images are good enough.

Having said that, you are really making good use of what you have and I believe you can really go far in proving naysayers wrong. People like you inspire others who are not disposed to spending a lot of money on the hobby and doing things the "acceptable" way. Sometimes, it almost seems like a competition of who has the deeper pocket. So, I feel your pain.

It's not anger....just sick of hearing "you need better gear". Does anyone believe that if we all had limitless funds we would be using the "lower end spectrum"? I suppose once you reach a certain age in life the "buy, buy, buy" talk becomes mundane......'coz I've heard it so often. Same with cars/phones/motorbikes/PC gear/software...etc.

Trouble is that there's not much point buying fancy "whatever" if you don't know how to use it, or drive/ride it. Same with where one lives in the world. Not much point having a Mclaren road car if the roads are pure crap! or a high performance bike. In Ireland the weather is just rubbish. We are lucky to see the sun for about a month in the year, and that goes for clear skies also. If I had clear skies for around 3 months in a year I would consider buying upgraded gear. I was just lucky the last week........we had a surprising spell of good weather. Last couple of days have been hailstone, thunder/lightning, rain, and cloud........and that is typical Irish weather.

There is also the problem for newbies to astro concerning shops/sellers advertising set-ups that are not really suited. When I first started to "invest" and get my first "decent" set-up, I opted for the skywatcher 8" dob on an eq5......which I still have. The advertising states a perfect match, but when you say the gear you have, you get, "that's nearly maxing out the mount". So if that's the case, how is it the perfect match?

Same advertising for the startravel 120......"great for photography of deep sky objects, but not planets".

If we cannot get the truth from those that sell, we are pretty much stuffed. Yes, we have forums like this one in abundance, but conflicting remarks just add more mis-understanding to new people.

When you ask a seller about photography through a dob they never, (or rarely), say, "you will need to move the mirror"......and that's because no-one wants that hassle, so they say, "yes, you just need to get the back-focus correct with extension tubes". CHING CHING.......sale made.

 

No, there is no harm pointing out something if that was asked. I never asked about CA, I was asking about FF's, but was met with basically, "don't bother". That is now a comment in the past, although I do believe in giving my view on the comment.

The CA is less with less light pollution came from me via an atp site on the net.......again, conflicting remarks.

 

I just went into Gimp with my photo, (after reading about removing CA from pics via Gimp), and it certainly works. The halo can be removed quite easily....but elongated stars cannot. I might, (might!), just treat myself to another scope so that getting a FF would be worth it. I will look into it. Even NASA photoshop and clean up their images, so maybe they need to get better equipment...lol

 

So it's not anger, just sick of being remarked upon to get something else. Maybe NASA can share their millions of dollars each year with those of us that do not get massive hand-outs?....lol

 

Anyhow, it seems that the synscan hand controller does not like me adding an extension lead to the ethernet port that is on the control box, it seems to lag, but I used a telephone line extension to the other port on the hand controller and that seems to be fine. The hand controller cannot be done away with unfortunately. Even with a USB-ethernet cable, it still has to go into the hand controller. Just means the hand controller stays with the tripod instead of inside with me. So I will keep the serial to usb adapter I currently have....it works fine.

 

Anyhow, I do enjoy a chin-wag....so I tend to become lengthy with my comments the deeper the discussion goes. thanks for your words.


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#19 Hook

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Posted 29 July 2021 - 07:17 AM

I am rather new to Gimp. I started using photoshop back in the 90's when you could get it on disk, but with it now only being on the web, and rather costly, I choose the free ones. Been doing some experimenting with it this morning. Most of the CA has now gone. I found this "vignetting" tool which I had a go at, which got rid of the furthest corners. Maybe I need more trials to find out how it works to the best......(I know I do need more trials).

 

There is so much to try out in Gimp I reckon it will be a long haul.

 

Thinking last night, I weighed up the pro's and con's of new gear. I like the william optics redcat 51. No FF to get and seems a very nice scope. 1000 euro is a lot of money for something I will use a month a year. So the purchase of a FF? There is no FF specific to my scope, but the hotech seems the best for me at 250 euros. The other option is to stick with what I've got, buy a drawing tablet and concentrate on "manipulating" my images.....like NASA. Decent drawing tablet with screen is 400 euros.

 

It sticks in my throat buying another scope, as I was "misled" by sellers into getting my 2 that I have already, and I would really need to sell them, (which in Ireland is not easy).

 

So for your pleasure, I include the latest attempt as stated above. It's not a "DaVinci", or a "David Bailey", but just showing how an image can be manipulated if you know how.......and I'm only scratching the surface.

 

andromeda test 1.jpg


Edited by Hook, 29 July 2021 - 07:18 AM.


#20 vidrazor

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Posted 29 July 2021 - 07:44 AM

I am rather new to Gimp. I started using photoshop back in the 90's when you could get it on disk, but with it now only being on the web, and rather costly, I choose the free ones. Been doing some experimenting with it this morning. Most of the CA has now gone. I found this "vignetting" tool which I had a go at, which got rid of the furthest corners. Maybe I need more trials to find out how it works to the best......(I know I do need more trials).

 

There is so much to try out in Gimp I reckon it will be a long haul.

 

Thinking last night, I weighed up the pro's and con's of new gear. I like the william optics redcat 51. No FF to get and seems a very nice scope. 1000 euro is a lot of money for something I will use a month a year. So the purchase of a FF? There is no FF specific to my scope, but the hotech seems the best for me at 250 euros. The other option is to stick with what I've got, buy a drawing tablet and concentrate on "manipulating" my images.....like NASA. Decent drawing tablet with screen is 400 euros.

 

It sticks in my throat buying another scope, as I was "misled" by sellers into getting my 2 that I have already, and I would really need to sell them, (which in Ireland is not easy).

 

So for your pleasure, I include the latest attempt as stated above. It's not a "DaVinci", or a "David Bailey", but just showing how an image can be manipulated if you know how.......and I'm only scratching the surface.

 

attachicon.gifandromeda test 1.jpg

Well you're losing detail there. You should try Siril out, it has a gradient reduction tool built in, as well as some really good additional processes, and it's free. You can probably also regain some of your core as well  You may also want to look into Affinity Photo, a good alternative to Photoshop which also has adjustment layers for non-destructive processing, as well as some astrophotography tools such as stacking and background removal. It's non-subscription and only costs 42 euro, a one time fee. They also have sales from time to time at discounted prices. You can download a trial to see how you like it.

 

As for scopes, there's a lesser-known wide field scope in the Red Cat range, the Askar 40mm. It's 220mm f/5.5 triplet that comes with a triplet reducer/flattener that turns it into a 180mm f/4.5. Much cheaper than the Red Cat.
 


Edited by vidrazor, 29 July 2021 - 03:35 PM.



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