The Astro-Imaging Thread

[Epox75]

14 hours ago, Green Baron said:

That looks good me thinks, probably what the seeing permitted. I don't see much distortion in the picture, at least less than before. The blowups from the far edge show only a very slight coma. So maybe a few millimeters more and you are fine ? Yes, try the 105 (or 115mm ?). As usual the "generic" thing might have similar data compared to the original ...

Am a little jealous. Still cloudy here. But i bet the sky skill will be clear when the moon comes out again ...

 

I tried a lens correction in post processing, it works with the stars but after its use I can't plate solve the image, too much distortion. Here is the uncorrected, plate solved image: http://www.astrobin.com/296553/

I have still to try at 105/115mm (I will check) and also much closer, like 40mm. From the information gathered on CN getting closer softens the coma but gives less FoV. Anyway I think the best way to solve this problem, instead of buying accessories for my C11, is to get a new OTA. After a long research I think that a newtonian like this: https://stargazerslounge.com/topic/196073-tsgso-150mm-f4-imaging-newtonian/  - http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4762_GSO-6--Imaging-Newton---150-mm-Oeffnung-f-4---2--MONORAIL.html will be the right solution. I need a fast and small scope to learn properly how to do DSO imaging, it's cheap so I wont cry buying accessories like its coma corrector/flattener.  

I hope you can get a nice night soon, this spring sucks here by the way.... the past years I could leave the telescope outside when the forecast was predicting a week or more of good weather but this year I have to hope for a single night without clouds

 

Edited May 23, 2017 by Epox75

[Green Baron]

I've bought a lot of stuff at TS in München, including a 200mm/f5 gso newton, the ccd cam and the mount. My newton is ok, but probably i would guess not the quality of your C11. I would say that if you have found the right focus and distances for the corrector/cam/C11 combination then things will be nice. For me it was really millimeter work with the apo and reducer and took several nights. Problem was that numbers from the data-sheets of camera and reducer were more like general guidelines than hard facts :-) I had to vary several times until the aberrations were gone.

The cassegrain focus has an advantage: everything is in a line. Finding the right balance with a camera sticking out at the side can be frustrating if the mount is near its limit. Also i would expect that getting everything right at f/4 can be much more tedious than at f/10 or 6 because depth of field and the image focus is all narrower. Tolerances when collimating are also smaller.

You get a really big fov almost like a dslr with a strong telelens and you have a shorter exposure time, almost an 8th at f/4 compared to f/10.

[Epox75]

9 minutes ago, Green Baron said:

I've bought a lot of stuff at TS in München, including a 200mm/f5 gso newton, the ccd cam and the mount. My newton is ok, but probably i would guess not the quality of your C11. I would say that if you have found the right focus and distances for the corrector/cam/C11 combination then things will be nice. For me it was really millimeter work with the apo and reducer and took several nights. Problem was that numbers from the data-sheets of camera and reducer were more like general guidelines than hard facts :-) I had to vary several times until the aberrations were gone.

The cassegrain focus has an advantage: everything is in a line. Finding the right balance with a camera sticking out at the side can be frustrating if the mount is near its limit. Also i would expect that getting everything right at f/4 can be much more tedious than at f/10 or 6 because depth of field and the image focus is all narrower. Tolerances when collimating are also smaller.

You get a really big fov almost like a dslr with a strong telelens and you have a shorter exposure time, almost an 8th at f/4 compared to f/10.

I know, a newtonian has a lot of downsides but has also upsides that i like. It's very cheap compared to an apo and has more aperture, which is good for a light polluted sky. Collimating will be an issue and not an issue: my c11 seems to have a rock solid collimation. In 4 years I have never touched it and I am scared of doing so. Probably working the collimation of the newtonian will give me a knowledge that every amateur astronomer should have :). My mount is a workhorse and I have a 1kg guide scope that together with the guide cam will somewhat balance the filter/wheel camera train at the side of the scope. And who knows.. .maybe i can find a way to use its coma corrector on my SCT. And now that i think about it I just received today the ZWO ADC that I was planning to use for planetary. While it may not help with the coma matter, It may help me in reaching the right distance from the reducer since I lack a true extension. 

[_Augustus_]

Bought a 75-200mm lens for my Pentax P30T today at a thrift store for $20. If I get some more customers/win a raffle, I might start doing deep-sky photography before the end of the year...

[Dooz]

I took this picture of the orion nebula with my canon DSLR. The lens was a 75-300mm telephoto zoom lens. 

The exposure was 3.2 seconds and ISO 3200

The bow shape is visible but faint.

[_Augustus_]

So I'm committed now. Just ordered an older 6" mirror kit. Should be fun.

I'm going to construct the telescope while I grind the mirror. Will post progress.

[Green Baron]

Kool. You're hardcore.

I built model planes when i was young. All of them flew but i won't tell how far and how long.

Looking forward to your reports and the outcome !

 

[Epox75]

I'm on M 92 at the moment. If everything goes well I should be able to integrate enough data for a color image. I also brought the camera 9.5 cm far from the reducer. Tomorrow should be another clear night, I will redo M13 at 10.5 cm from the camera. Globular clusters are good to check lens distortion

 

[munlander1]

Lots and lots of clouds.

[Green Baron]

It was a steel blue sky all day long the last days. It has become sort of ritual: i carry everything out when the sun is low to let it cool down. Then short after sunset it starts to condensate around the island and a layer of clouds forms about 200m above my level. So i take the stuff in again. Early in the morning then, before sunrise, the layer starts to dissipate.

Above the layer, 1200m and higher, there is of course a magnificent sky.

If it is like this tonight i'll grab the small mount, dslr and a battery and drive up the mountain to do a little wide field.

[MaxPeck]

3 hours ago, Green Baron said:

It was a steel blue sky all day long the last days. It has become sort of ritual: i carry everything out when the sun is low to let it cool down. Then short after sunset it starts to condensate around the island and a layer of clouds forms about 200m above my level. So i take the stuff in again. Early in the morning then, before sunrise, the layer starts to dissipate.

Above the layer, 1200m and higher, there is of course a magnificent sky.

If it is like this tonight i'll grab the small mount, dslr and a battery and drive up the mountain to do a little wide field.

Do a google search for something called "clear outside" - it's a detailed astronomy forecast and it's saved me from a lot of sore backs carrying gear in and out of the house. 

[Epox75]

Tomorrow i'll post details about capturing/processing... these have been two very long nights. Yesterday successful, tonight a complete failure  I am very tired now, gonna get some sleep... meanwhile you can count the stars   By the way.. .it's M 92 the ignored brother of M 13. 

Edit: technical card - http://www.astrobin.com/296908/B/

The image was processed with pixinsight and maxim dl 4.5, using deep sky stacker only for the quality evaluation of the single exposures. Every exposure was calibrated using a superbias a master flat and a master dark. I found very useful the function Masked Stretch that brought out a lot of details without altering much the background. On maxim dl I applied a local adaptive filter to enhance details on the core and increased the saturation of about 30%. 

 

 

Edited May 27, 2017 by Epox75

[Epox75]

So... here it is.. the TS 6'' imaging newtonian aka the Battlescope. It's a toy, literally, but that's a pro and a con. I already bought some stuff (gaskets, springs) to reinforce the primary mirror cell. While collimation may hold while it's on the mount it goes off for sure while taking it down or putting it up. I already scratched a bit of paint while clamping/unclamping and moving the OTA to find balance.. and by the way it is very well balanced and it's very light I needed just one counterweight and it is all way up on the bar, my mount is gonna be very happy I believe.  Another thing that i noticed are light leaks from the back.. i had to put some black tape there and later on gaskets should do the job. So my verdict till now is that is sucks compared to my c11 but it may have potential. I have also read about chip illumination problems with the GSO imaging newtonian but that was a 5 years old post and this is sold by TS so we'll see about that...anyway if true I will also need to move secondary and focuser further up on the tube and that will be a more serious trouble.

Edit: So I did collimation for the first time ever, lol... and I was so scared about it. I will probably use the collimator on the SCT too and see what happens. I tried to slew the scope in various positions and the collimation didn't change as well it didn't change in a couple of hours of time.. .if think that is not so bad that little space between the tube and the mirror, it probably won't be affected by the metal tube shifting for temperature change. And the chip is fully illuminated.. so I can say that the telescope it's maybe good enough to do something interesting as it is. Unfortunately I cannot test it tonight .. clouds

Just a little thought about laser collimation, it's not hard but there are 1000 ways to do it wrong and one to do it right. In my case collimation must be done when the OTA is on the mount so it's basically impossible to have the gravity to assists you in putting the collimator perfectly horizontal in the focuser. So what i did was pushing the collimator very firmly against the focuser while locking it and after leaving it be is quite easy to tell if it moved or not.

From what I could see, my favorite method is to and loose all the screws/knobs of the primary a bit, start with the secondary mirror, put the ray in the center of the primary, start aligning the primary by tightening the collimation screws until they are completely tightened and the scope alligned. Then a second round, recenter the ray into the primary with the secondary screws, put the ray back into the center and then start tightening the locking screws of the primary until collimation is reached and the screws tightened at max. Then a third round of collimation will require a minimal adjustment of the secondary and then the primary by a very-minimal loosening of the lock screws. In this way you have reached collimation and you have the mirror locked  tight.  

 

 

Edited May 30, 2017 by Epox75

[Green Baron]

An umbrella stand :-)

For collimation (also with the laser pointer) turn the tube so that the focuser faces up. You could coil a bit of adhesive tape around the pointer so that it fits almost perfectly in a 1,25" opening.

And i'm doing the same ritual: first the main mirror, then the secondary mirror. But i never tighten the screws of the main mirror, just so far that it can be moved by hand in the cell. Nearly all of the instructions say so because of risk of mirror deformation when temperature changes.

 

[Epox75]

18 hours ago, Green Baron said:

An umbrella stand :-)

For collimation (also with the laser pointer) turn the tube so that the focuser faces up. You could coil a bit of adhesive tape around the pointer so that it fits almost perfectly in a 1,25" opening.

And i'm doing the same ritual: first the main mirror, then the secondary mirror. But i never tighten the screws of the main mirror, just so far that it can be moved by hand in the cell. Nearly all of the instructions say so because of risk of mirror deformation when temperature changes.

 

Lol, True! The scope came without detailed instruction, you mean the locking screws? The mirror is a heavy piece if I don't lock it I fear it will shift under his weight when the telescope turns. But anyway there will be tests   I hope for no clouds tonight. 

Edited June 1, 2017 by Epox75

[munlander1]

Not doing half bad on my current photos.

[munlander1]

Going to bed, started stacking and will check back in tomorrow (today).

Edited June 1, 2017 by munlander1

[Green Baron]

2 hours ago, munlander1 said:

Not doing half bad on my current photos.

*rubchin* hmm, that leaves us with two possible interpretations ....

:-))

[munlander1]

Stacking has been going terribly-

I have a grey photo with a white band now...

Edited June 1, 2017 by munlander1

[_Augustus_]

HA

HA HA

http://www.astrobin.com/297955/

[kurja]

1 hour ago, munlander1 said:

Stacking has been going terribly-

I have a grey photo with a white band now...

I would expect that to be caused by a problem in calibration, not alignment or integration, did you check that the lights were ok before stacking?

[Green Baron]

1 hour ago, munlander1 said:

Stacking has been going terribly- I have a grey photo with a white band now...

Well, if you want to inform us about the stripes, ok, information received :-)

I assume it's your nexton + eos400d and the screenshot is from the stacked lightframes after application of dark and bias ?

Type, number and exposure time as well as settings like temperature and iso of the cam if applicable ?

How many frames do you have, light, dark, bias flat ? How are single frames ? If you stretch (histogram gamma curve) a single dark or a single light frame, does it show stripes as well ? A slight readout error from the chip sums up over multiple exposures because the program cannot distinguish is from e.g. a nebula if it doesn't have a hint. cmos chips are more prone to these errors (horizontal or vertical stripes) than ccds because they are produced for single shots where these errors don't matter.

If you don't see them on single darks or biases, do the stripes appear on the master dark or even the master bias as well if you stretch the histogram or just on the stacked lights ? If yes then it is something with the camera / chip, if no it might be an artefact from the stacking.

Then try other settings while stacking, if you have like 10 frames or more of each light dark and bias try sigma-kappa stacking in dss because it weighs single exposures less. If it turns out to be a chip error than you will need a software like PixInsight (and a semester of intense study) to correct it.

 

[munlander1]

1 hour ago, Green Baron said:

I assume it's your nexton + eos400d and the screenshot is from the stacked lightframes after application of dark and bias ?

Yep, my Newton with my cannon and my Newton. Was only stacking lights because dss was acting up again.

1 hour ago, Green Baron said:

Type, number and exposure time as well as settings like temperature and iso of the cam if applicable ?

 

JPEG (forgot to switch to raw), 43 exposures at iso of 1,600.

1 hour ago, Green Baron said:

How many frames do you have, light, dark, bias flat ? How are single frames ? If you stretch (histogram gamma curve) a single dark or a single light frame, does it show stripes as well ?

43 Lights, 25 darks, no biases. Single frames are somewhat noisily with comma around the edges of the photos. Lights are fine. Stacking a dark and the master dark as a light left me with lines. 

1 hour ago, Green Baron said:

If it turns out to be a chip error than you will need a software like PixInsight (and a semester of intense study) to correct it.

Would the error be unique to the chip itself?

[Epox75]

So here's part of the 1st light of the Battlescope... 38 minutes (19x120sec) with lumicon deepsky filter on the Elephant's Trunk Nebula. 

The coma corrector I use is The TS-Optics GPU superflat 2" Coma Corrector for Newtonian telescopes, 4-element and the technical sheet says: 

♦ Focal length up to 600 mm - working distance 51.50 mm
♦ Focal length 610-800 mm - working distance 53.50 mm
♦ Focal length 810-1000 mm - working distance 55 mm
♦ Focal length 1010 mm - working distance 54.50 mm

My calculations says that I'm 56.50mm far from the corrector and I have a focal of 600mm,  I ordered a set of extension (20mm, 10mm and 5mm) so I should be able to reach the right distance, I own a 30mm extension and is too long. The donut you can see at the center of the picture is caused by the badly covered rear cell:

 

 I mean is cool to see the donut fully illuminated from the collimation laser when you look at the back of the scope but at least provide me some cover! Anyway problem solved: 

 

And about collimation: I might have been slightly off in the picture. I made a sort of cheshire drilling a hole on a old diagonal cover cap and I noticed a slight offset of the secondary. While I was adjusting the screws I felt that one was very hard so I took some calipers.... and I ended up bending one arm a little.. fortunately and with enough obsession I managed to undo the bending, loose the screw and solve the offset of the secondary. So I did collimate the scope with the cheshire and did a counter test with the laser.. which seems to confirm the correct collimation only when the collimator's 45' inclined surface was parallel to the secondary mirror surface.  ( /   ---->   / ). Could be high-precision or slight offset of the collimator, this I don't know, but I'm happy I figured it out. Another thing to fix is a light leak from the focuser, I spent more than 1 hours trying to take darks but always seeing a leak, in the end I understood it was the focuser, where the locking screws are, that's normal I guess.

So overall I like the scope, the optics are good, the focuser is very good, the build is poor but from what I've seen It holds collimation and I still have to improve that aspect by installing new springs, which of course I won't do until I find it necessary. Also a dew shield is incoming for protection from stray light. 

LOL! I Just realized that I was 21,6 mm from the coma corrector and not 51,6! I forgot the extension!

 

 

 

 

 

Edited June 1, 2017 by Epox75

[munlander1]

Processing has smeared the stars, but the arms are visible.