Ken Mitchell

When your post processing knowledge expand I find it interesting to go back to old images and see what results you can now pull off with that data.

Decided to take on a 2018 image, the first time I imaged Andromeda with my new refractor back then. 

Processing went much faster and easier as before. This also might be the version which I prefer the most, I believe it's the fourth version so far. Every one had something to it but imo this has the most 'natural' look . Also in previous versions it was difficult to pull out the colors but with this edit all they 'appeared' during the stretching with very little need to use color boosting tools.

I'll post the previous versions in the comment below if you want to see the 'progress'. 

The difference with this stack is that I used the drizzle function and custom rectangle in DSS, I thought it would be beneficial as my setup is slightly undersampled, any information on how and when to use drizzle is welcome.

The most obvious error in the image here are the startrails, which is unfortunate, but as I said it was the first time on Andromeda with this scope and the fourth target with this scope. Didn't had everything figured out yet, max exposure time, balancing and such. 

Seeing these new results I'm waiting for Andromeda season again and take on that galaxy again, this time with guiding.

Here are some details on image and equipment:

-

Nikon d610 stock
TS72 APO + TS72flat
settings: 432mm, f6, iso1600, 6.5hrs (60ec subs)
-
Tracking: Skywatcher Star Adventurer unguided
software:
Stacking: Deepskystacker 4.2.2 (drizzle2)
Processing: Adobe Photoshop,  several PS plugins and astro actions

Ken

On 19/02/2020 at 11:56, Z3roCool said:

Wow, that is brilliant. Going to have a go at this.

I live in a pretty LP area. Normally shoot NB. Have got LRGB filters, do you think it will be worth it with a 1600MM and 400 camera lens?

Definitely worth it yes. You can also wait until May when the comet is at its brightest.

Ken

23 hours ago, Davey-T said:

Excellent Ken, I took some shots of it around the same time but haven't gotten around to looking at them yet.

Dave

Thanks Dave! Yeah I was too excited about the comet so the processing went rather quickly  

Hope you get some good data. What equipment did you use?

Ken

9 hours ago, adyj1 said:

Thanks a lot for the info - I have a Walimex 85mm 1.8 and this gives me a good starting point... 

No problem.

I've never used the Walimex though, so you'll have to do some test for yourself to determine it's best f stop. I imagine there will be some differences but from what I've read it's a really good astro lens and many shoot wide open with it, even better :) 

Ken

6 hours ago, adyj1 said:

Awesome!

Did you have the aperture stopped back at all, or was it taken at 1.8?

Just had a look at the raw and I stopped down to f4 and used iso 400 on the camera. At f1.8 the lens has some coma in the corners and a good amount of vignette.

At f2.8 the coma is mostly removed but I'm not too happy with the amount of vignette. f4 did the trick for me.

Ken

Video of the individual frames captured that night

Hi all,

My first capture of a comet and pretty exited about it! Definitely makes you think!

Love to get back to this rock in couple months to get a composition with the H&S nebula and hopefully with a bit more brightness. Curious at how it will look then!

This was just over two hours of imaging using the stock Nikon d610 and TS72 apo.

Mounted and guided with the Star adventurer.

The image is a blend of two stacks, one aligned for the stars and one for the comet. Stacking was done in DSS.

Ken

Hi all,

For a long time I wanted to shoot this frame, probably from the early days of my astrophotography adventure.

Finally after all these years I managed to get a decent result of the 'stuff' between these two beautiful nebulae. Fairly happy with the image but always looking for improvement.

I hope one day to redo this all with a mono camera and filters. 

Apart from NGC1499 , M45 and the Baby Eagle Nebula no idea what else is in the picture. If you happen to have an idea feel free to educate me.

Some info on image and capturing:

Widefield Pleiades to California.

Taken over 2 nights with a total of 11hrs 25min integration.  

With a stock Nikon d610 and Nikkor 85mm 1.8 objective.

Tracking was done with the Skywatcher Star Adventurer.

Lights and all calibrations frames were stacked in DSS.

Processing was done in Adobe Photoshop CC using Adobe Raw, GradientXterminator plugin, HLVG plugin, Nik software plugins and Photokemi action set.

Ken

22 hours ago, Owmuchonomy said:

The place to start with this is to work from your camera pixel size (3.75 microns); times that by 4 or 5 and aim for that f/ratio.  So the sweet spot for your camera is around f/ 15 to 19.  Choose a Barlow or Powermate that gets you in that region.  The other way you can increase the level of detail (without changing scope) is to switch to a Mono camera used in conjunction with an IR pass filter.  My best Moon images (see link below) were obtained with either an ASI174 or ASI290 mono camera.  The 290 has particularly good near IR sensitivity.

That's interesting, thatks. So the best one would be a 2.5x or should a regular 2x be ok?

I found the Baader Hyperion 2.25x or the ES focal extender 2x(What Craig recommends) The 2.5x Powermate is just a bit high in price.

Any thought on those?

Ken

12 hours ago, CraigT82 said:

I've never had any problems with mine.

Is there any advantage choosing the 2" before the 1.25"?

Ken

3 hours ago, CraigT82 said:

That's a really nice image! I personally use the 2x and 3x explore scientific focal extenders and I find them both excellent 

Do you refer to this one?

https://www.astroshop.eu/barlow-lenses/explore-scientific-barlow-lens-focal-extender-2x-1-25-/p,54035

Does a focal extender like that introduce vignette or softness in the corners?

Ken

Hi all,

I'm looking for recommendations on barlows for imaging. I'm using a 72mm refractor with asi120mcs and would like to take close ups of the Moon's surface without changing the scope.

Is this possible with barlows or are they only for observing?

If so, is there anything worth buying for around $100-$150?

 This is my latest image, 2 mosaic form 2x 4000frames.

As you can see there is some detail in it but not as much as I like.

Thanks

Ken

One of my latest image, M78  with some Barnard's Loop, Sh 2-276

TS72 APO + TS72flat on a Nikon d90(mod)
432mm /f6/ iso800
2hrs.50min

Tracked with the Star Adventurer 
TS 50mm f3.6 guidescope connected on a zwo asi120mc-s

Stacked in DSS and processed in Photoshop

Hi all,

I've decided to take another small step up on the astro ladder. Going from dslr to dedicated mono astrocam.

My primary goals for the future are taking very wide angle shots containing different dso's but with the addition of the 'stuff' in between them. Molecular dust, dark nebula, integrated flux nebula,...

Which filters would I need to do that. Already have a 7nm Ha and might get an 8nm Olll, primarily for the dso's. I know narrowband won't capture the dust , ifn,... so was wondering what would I need in order to get this detail added?

Can I just shoot with the mono camera or lum filter to get this data or will I need a full rgb filter set?

As an example of my goals I add a recent image I captured with a dslr. I was hoping a mono camera would give me better results and also shorten the total exposure time comparing to a dslr.

I'm open for suggestions

Thank you 

Ken

One of my latest images with the Star Adventurer, the Blue Horsehead Nebula. 

Nikon d610 camera
TS-Optics Photoline 72mm FPL53 APO with 
TS-flat72
Tracked with the Skywatcher Star Adventurer 
TS 50mm f3.6 guidescope connected on a zwo asi120mc-s

Total exposure time: 7hrs 56min,
iso800 f6

Stacked in DSS
Processed in Photoshop

5 hours ago, Davey-T said:

Excellent image Ken, how dark are your skies ?

Dave

Thanks Dave!

Bortle 4, close to bortle 3. 

Ken

Image from October.

Iris Nebula and Ghost Nebula somewhere in Cepheus.

Nikon d610
432mm /f6/ iso1600
Total 3hrs 33min 212frames 
Stacked in DSS and processed in Photoshop 

On 16/11/2018 at 21:58, kens said:

The trails are in declination so they are actually caused by non-guiding  This illustrates why you need very good PA when not guiding in declination. Its a bit hard to tell from a JPEG but it looks like you've got about 3 pixels of drift per subframe.The pixel scale is 8.6 as/pixel so that's around 25 arcsec of drift. You didn't mention the length of the subs but assuming 5 minutes that means your PA error was in the order of 30 arcmin which is quite large. Now that you've got PHD2 running I'd suggest using its drift alignment tool to improve your PA. That will help you get more detail since they wont be smeared.

I'm not familiar with using a DSLR with HA filter but I imagine you'd want to take a set of subs with no filter to make up a synthetic lum channel and another set with the Ha filter for the nebulosity. For the no-filter case, doubling the integration time will improve SNR by the square root of 2 (1.4x). With the Ha filter you'll get light on only 1/4 of your pixels. Plus at 7nm even the red pixels will be getting just a small fraction of the sky background - in the order of 1/14th. That will affect how long you need to expose each sub. 

 

Short follow up and thanks.

Sorry for the late reply, had some issues with my guiding laptop. It gave up on me so had to get me a new one for guiding.

Also still waiting for the new desktop to arrive in able to do post processing.

Neither did I had the opportunity to do more testing with phd2 or the SA. When all is back to order I will definitely continue this to improve my imaging and acquire more knowledge on the topic in general. 

Ken

Out of curiosity I did a stack from last night's subs without calibration frames and simple edit in photoshop. Total was just over 3hours.

At the bottom there is a 100% crop to see the trails caused by the guiding.

Should I give this another go? With double the exposure how much more detail should I get on this target.

Or is it best to wait and do this with my modded cam and 7nm Ha?

Ken

Thanks a lot for the help!

Last question(for now), even if the Star Adventurer doesn't guide in dec it is still important to enter the correct dec degrees? Will these values be taken into account when correcting for RA?

Would you happen to have some information on how this operates, just to have an idea what phd is doing.

Ken 

Ok gotcha. I understand now.

I assume you can consult the dec degrees with Stellarium or similar SF? So for every target I image it is best to change the dec degrees in phd2?

Ken

9 hours ago, kens said:

When you are connecting click the settings button as shown and you'll get the options for 8bit and 16bit

NGC7822 is at dec 67 which is not very extreme although PHD2 recommends against it. At that declination the RA pulses need to be 2.5x longer than at the equator for a given movement. In the step size calculator make sure all the values are correct and enter the maximum 60 degrees declination. Then manually add 25-30% to the calculated value.

When you are very close to the pole (say > 85 degrees) you can turn off RA guiding 

You'll also want your guide star to be close to your target as the relative motion difference between the two will be greater if they are at different declinations. You also want to be sure not to chase the seeing as your mount will be making large movements in RA to correct for small star movements on the sensor.

These are the default values, I only changed the FL. What values should I change here?

Do you suggest I try to turn of guiding for that target and see how well it performs?

Ken

16 hours ago, kens said:

If you are not guiding in Dec then you do need very good PA. As a guide the amount of drift you get will be equivalent to the PA error over a period of 6 hours. If you want less than 1 arcsecond of drift on a 5 minute exposure your PA needs to be in the order of 1 arcminute. You can use PHD2s drift alignment tool to adjust your PA.

Getting a good focus on the guidescope will help a lot. Is there a focus ring near the objective lens you can use? Also, since you have the ASI120 you may be able to use a threaded connection. Then you can use spacers to adjust the focus.

To choose a guide star you can either let PHD2 choose one (Tools > Auto select star) or if you do it manually, display the star profile and ensure that it does not have a flat top. You can adjust the camera gain if there are no suitable stars. Also, when you connect the camera, select 16 bit mode. It tends to give better profiles for guiding.

Since you are not guiding in Dec the guide star does not need to be very close to where you are imaging. Obviously not pointing 90 degrees away or anything like that but within a few degrees wont make much difference. 

Thanks for the information. Where do I choose 16bit mode? Can't seem to find it.

Would you happen to have any advice on guiding while imaging targets close to the celestial pole? Obviously you can't choose Polaris but even stars in the vicinity don't work. Calibration fails because the star didn't move enough. And when I choose a star somewhat off axis from where the main scope is aiming I get startrails. I don't think it's because "bad" PA but rather because the guide doesn't compensate correctly for the guidestar is off axis. Could that be?

My target is ngc 7822  if that helps.

Ken

New one from the last 2 nights and second time using guiding with the SA.

All went well except for the winds on night 2 which gave some vibration to some of the frames and didn't include 50 minutes into the total integration. Might put a heavier load on the tripod and see if it will changes things.

First night got 39 frames of each 5 min and second night 38 frames of each 5 min. A total of around 6hrs and 20min.

TS72 APO + TS flat72 with Nikon d610

77 x 5 min guided

Tracked with the SA and guided with TS 50mm mini guidescope with asi zwo 120mc-s

Stacking was done in DSS and processing in Photoshop.

Ken

On 11/11/2018 at 21:50, kens said:

Looks like the Star Adventurer will only accept guide commands whilst in celestial tracking mode so you can't test it in daylight.

PHD2 will start calibrating automatically when you start guiding. For RA only guiding you need to turn off Dec guiding as shown below. Also, you can find the PHD2 manual at https://openphdguiding.org/manual/?section=Introduction.htm

Personally I would not recommend using PHD1 as it has not been supported for many years now

Managed to get it up and running and had some decent guiding results I believe.

Got up to 5 min without startrails. Did a few tests yesterday night to see how well it reacted to a good or bad PA. I've heard people say you can do a rough PA and still get good guiding. Maybe that's true for a mount that guides in both axis? but from what I've tested it seems that it's pretty important you have a good PA with the SA as it doesn't guide in dec. 

My PA was slightly off and got trails even with 2 minutes. I could see the guidestar drifting, as with a good PA the guidestar stays in the middle. Probably because the SA can't compensate for dec.

The things that are most difficult in the guide process is locking onto a guidestar and getting focus right with that particular scope. I now wish I'd payed 50$ more and get the one with the microfocuser. The one I have now is push and pull and find it a bit hard to operate. 

Any tips on choosing/acquiring a good guidestar? It seems like it's not always the best option to choose the brightest in the sky, or am I wrong? 

How important is it to choose a star in roughly the same area you're imaging in?

Ken