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First light M42


Magnus_e
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Hi all stargazers :)

This weekend i made my first attempt at astrophotography, and i must say i got more than excpected :)

Of course. Being my first attempt there ar loads that can be improved, and i'm looking forward to do so.

I thought i would post a thread here and see if i could get some pointers for my next attempt.

Looking at the picture "a bit zoomed in" its easy to see a kind of triangular shape on most of the stars.

I'm not shure if this is because the image is out of focus, or if there are some other resons. I'm thinking that it's a focus issue, as the less bright stars are more like halos than points.

I also have a question about calibrating a equatorial mount using DARV.

The steps i used:

Level and point the tripod north.

Attach the mount, and adjust the altetude to my location's lathetude.

Do a quick aling on the mount "so it's tracking earth rotation".

Point the scope at a bright star an slew the Ra axis across the camera sensor.

      "rotating the camera until the star slews in a horizontal line: 'framing' ".

Point the scope towards the south median, and to a star as close as possible to 0 deg.

     Move the star to the left of the image frame.

     Take a 125 sec exposure. Wait first 5 seconds to "burn" a start reference.

     Slew the star to the right of the image frame for 60 seconds, then slew 60 seconds back to original position.

     If a < line is visible on image. Adjust azimuth axis and repeat until you have a strait line on the image.

Point the scope directly east or west and as close as possible to 0 deg.

     Repeat the step above, adjusting the altitude axis on the mount until a strait line on the picture.

Are these the right steps? I'm guessing tha because it's the alitude and azimuth that is being adjusted on the mount, that 0 deg == the horizon?

If this is correct then i had a feginners fluke and assembled the mount perfect. I never did get a < line?

I also had a problem that when i told the mount to goto m42 then it was pointin about where m42 was one hour back in time. I had to slew manually to find

it, but that was not to hard. Could be that i messed up some settings in the menu?

So then the result :)

Stacked in deepskystacker with 2xdrizzle, and a little edited in photoshop.

Here it's easy tho see the "triangular" stars

gallery_42115_3630_380446.jpg

This one is only corrected in dss without drizzle

gallery_42115_3630_99053.jpg

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Welcome to the fun world of AP! 

Nice picture as well!

I think you are right about the focus being a little out. Also, M42, although one of the easiest DSO's to 'image' is also one of the hardest to make look good due to the dynamic range. In your picture above, the core of M42 is blown out. What people normally do with this is take some extra short exposures and blend them together. 

However, you have caught a lot of detail in the outer regions, and a running man in there as well! 

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Excellent beginnings! Edit looks great with great colors. The focus looks just a bit off to me besides the irregular shaped stars. You might want to also check that the optical chain is all lined up properly. Maybe you need a field flattener with your scope? Some refractors have these built in some don't. That said again well done I say and keep shooting for the stars!

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Great start with that image I am guessing that you are using is a well corected ED doublet of more likely a triplet with a focal length of about 400mm, I agree with the comment about pinched optics especially in a triplet with the nominal 3 point lens mounting/adjustment but the issue may be caused by not allowing the tube to cool adequately.

The focus is as you suspect a little off but have no idea what the camera/focusing method is so cant advise but I would say there is far more good things than bad with the resultant image and nothing that cant normally be fixed easily.

Alan

Edited by Alien 13
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Great picture. I'll leave the shape of the stars to the experts, but I was also having trouble with halos. Check your subs and see if the halos appear there as well. If they don't then you might want to try turning off the DETECT AND CLEAN REMAINING HOT PIXELS and DETECT AND CLEAN REMAINING COLD PIXELS in the COSMETIC tab. I was having trouble with halos post stacking and this cured it!

Great pic!

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Hi.

Thanks for the replies. Wil have to check my notification settings, cause i did not get any.

The ota i'm using is probably not the best suited for a main imaging scope.

I was shopping the web with my eyes and not my wallet, so i was planing on a newtonian astrograph. I narrowed it down to the Orion 8" f/3.9,

with the short tube autoguider. But as i realized i was stretchin my budget to far i actually now got the Orion Short Tube 80mm f/5 as my main scope :)

It's only an achromat and no ed glasses.

I see that happy-kat mentioned pinched optics. As i wanted the autoguider kamera i bought the autoguider version of the short tube, and the rings

that comes with it attaches to the skope by three thumbscrews. It might be that it is causing the triangle stars? Two normal rings would probably not

kost to much, so i might try that to see if it fixes it.

I did have the clean hot and cold pixels enabled. I'll try to re stack it and see if it helpes.

I uploaded one sub converted to jpeg, so ill post it here. It got resized when i uploaded it. Looks like there is a little trailing. Not shure if it's the best sub.

gallery_42115_3630_4272070.jpg

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I love my ST80 scope.

There is a guide on astronomyshed about fine tuning the ST80, you might like a look at that. My little 70mm tube had pinched optics so tight it took me ages to get the lens cell retaining ring loose so that I could then just finger tighten back up.

May be all you need to do is carefully loosen off the lens cell retaining ring and then gently re do it finger tight back up again. You might find the lens cell ring is tight tight on the end.

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Thanks for the tip. Think i found it.

Just took a look at the stars in the subs in dss, and i did not see the same halo effect.

The larger brightest stars had a blue glow around them, but they did not have black centers.

Started a new stacking session without DETECT AND CLEAN HOT / COLD PIXELS.

Would be amazing if it helped.

Just an other beginner quesion. Could i just from now and into the future collect all raws that i take,

and eventually end up with hundreds of long exposed frames to stack? Then every time i feel i have

improvements stack a new version. Or will i get a better image just stacking the newest and best frames?

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Just as a test to disable CLEAN HOT / COLD PIXELS.

The image got to cold, so i will try again but the round triangles in the middle of the stars is gone :)

Thanks for the tip Star Forming!

Wil try to improve on the saturation and wb and see what i get :)

gallery_42115_3630_494513.jpg

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Hey Magnus, glad it helped - hopefully the tips about pinched optics will help with the shape of the stars too? Check out this thread:

http://stargazerslounge.com/topic/235929-had-a-go-at-the-orion-nebula-last-night/

Which is also about Orion - I posted my work process in DSS for stacking/settings and it might help. Everyone does this stuff differently and a lot of it comes down to taste, but give it a whirl and see what happens!

As for stacking hundreds of subs, I am not sure if that is going to make much difference. I am still a novice, so don't take this as gospel, but I have been reading (in more than one place) that perhaps 30 subs is the point at which the returns in quality diminish quite rapidly in relation to the additional number of subs. Again, everyone has a different approach and it may be a different story once you are using CCD cameras, guiding and stacking exposures of 10 minutes plus. You can stack lights from different sessions - I've played around with it in DSS myself, but I was not convinced that it made a great deal of difference but, again, have a play, and see what happens - can't do any harm! And, if you are trying to take suitable subs to blend the core, you may end up with subs from different sessions.

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So, after using the feedback i have gotten about the picture, and the hot / cold pixel tip.

I have edited the new stack in deepskystacker and photoshop.

This time i did use the lumonosity sliders in dss more, an got the overexposure in the

middle down a bit. Then i further worked on it i photoshop with curves and layer masks.

Let me know what you think :)

gallery_42115_3630_492169.jpg

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Nice work. That reworked image looks vastly better. I'm wondering if the triangular stars are just a bit of trailing due to misalignment.

Are these the right steps? I'm guessing tha because it's the alitude and azimuth that is being adjusted on the mount, that 0 deg == the horizon?

If this is correct then i had a feginners fluke and assembled the mount perfect. I never did get a < line?

I also had a problem that when i told the mount to goto m42 then it was pointin about where m42 was one hour back in time. I had to slew manually to find

it, but that was not to hard. Could be that i messed up some settings in the menu?

0 degrees is the celestial equator. My usual approach is to start with the scope in the home position (pointing at the pole) and slew to 0 degrees declination. You are then pointing at either the East or West horizon. I prefer east. This is the position for the altitude adjustment. But before I do that I like to adjust for azimuth first since it is more likely to be wrong and I don't want it to mess up the altitude alignment.

So from that position pointing at the horizon  I rotate in RA till the counterweight is near horizontal leaving dec at 0 degrees. You are then pointing at the intersection of the equator and the meridian and can adjust for azimuth.

As I said, I then return to the horizon, slewing in RA leaving dec at 0 degrees and perform the altitude alignment

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Thanks for the tip about the polar alignment :)

Will try to use that method next time. How do i slew to 0 deg.dec? Can i do this in the handkontroller? I have a nextstar + "and a german manual :)"

The photoshop plugins looked a bit expensive. Might get them at point in the future :)

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Hi all stargazers :)

Are these the right steps? I'm guessing tha because it's the alitude and azimuth that is being adjusted on the mount, that 0 deg == the horizon?

Zero Degrees DEC is not the horizon.

It arrives at the horizon directly due East/West.

Due South it will be some way above your horizon depending on your Latitude.

Here in the southern UK it's around 40 degrees in elevation.

When I do the East routine I pick a star thats on 0 DEC thats about 20 degrees above the horizon

as I cannot see my East or West horizon, I usually do I longer exposure just to make sure.

BTW Zero degrees DEC is the celestial equator.

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As i learn more what to loock for, i see that there are some strartrail in the subs.

The  attached picture shows a star with a trail on it. Ortherwise the star looks round.

Maby the triangular shapes it due to trails being stacked?

It was really cold and windy when the picture was taken and i could not find the tracking options in phd.

Is dec tracking enabeled by default in phd? If not i might have had a less than perfect polaralignment

and ended up with some trailing? I have heard enabeling dec tracking and selecting north or south

should help with that.

post-42115-0-76459800-1423821777.jpg

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Have a close look at a single sub, do the stars look triangle shaped?

The single star above is a single sub. And looks more trailing than triangular :)

Maby all stars will be round if i follow the tips above on polaralignment, and enable dec tracking in phd if it's not enabled by default.

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I tried to google what a CA ringed star was, but didn't find anything emedeatly :)

I did fint two stars thar vere triangle and small on the first stack. I'll add both the stack and the sub.

The subs are 1 480 sec iso 100, 7 540 sec iso 100, so about 1h10m exposure.

Also have 4 dark 540 sec iso 100

11 bias 1/4000 sec iso 100

and 20 "t-shirt" flat 1/30 sec iso 100 taken at daytime.

post-42115-0-86445000-1423827505.jpg

post-42115-0-31426700-1423827515.jpg

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There are two types of CA.

Longtitudinal CA puts the coloured rings around the star.

All stars across the field will most likely look the same.

Lateral CA has red and blue offset on each side of the star, with the elongated star pointing towards the centre of field.

Nearer the centre the stars my look ok.

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There are two types of CA.

Longtitudinal CA puts the coloured rings around the star.

All stars across the field will most likely look the same.

Lateral CA has red and blue offset on each side of the star, with the elongated star pointing towards the centre of field.

Nearer the centre the stars my look ok.

I found some stars wit Latheral CA near the center of th image i think ?

post-42115-0-57970300-1423832549.jpg

post-42115-0-65817100-1423832559.jpg

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