[cheekygeek]

I have not had success with mine yet, but I first suspected a poor mount (very small and cheap ballhead) and then (after correcting that by getting an Arca-Swiss p0 monoball) I suspect user error.

How do you determine the proper exposure for your sub-exposures? Do you want the histogram spike to be just off the left edge?
Do you find that the menu is wildly over-optimistic in what it says your maximum time of exposure is possible?
I shoot in RAW+, is that OK?
Are you going to see results in the JPEGs or only after you have stretched the histogram in post-processing?
Do you turn Auto-ISO off?
What about noise reduction?
Any other camera menu settings that I should change?
Any tricks for "locking down" your lens focus once you have it? (I'm using manual lenses... trying the K 135mm f2.5 (at f4)

Sorry for the question dump! Thanks for any replies. I hope to take another run at it tonight.

[Digitalis]

I have had some good luck with my Sigma 100-300mm f/4 APO EX DG on my K5IIs - though I have had issues with calibration.

[gleeman]

How do you determine the proper exposure for your sub-exposures? Do you want the histogram spike to be just off the left edge?
Do you find that the menu is wildly over-optimistic in what it says your maximum time of exposure is possible?

>>because most the deep sky objects are faint, so i always try to overexpose a bit (just touch the histogram right edge)

to image a faint DSO , I usually set the exposure time at 120sec first (K5 w/ DA*200), then adjust the exposure by changing ISO(mostly) or trace time .


I shoot in RAW+, is that OK?
>>That's ok

Are you going to see results in the JPEGs or only after you have stretched the histogram in post-processing?

>> I always check the object on camera's LCD after every shot, (mostly)You can see the object in image (LCD)
even if the image is full of light pollution. (as attachment image)



Do you turn Auto-ISO off?

>>Auto-ISO Off
I usually set ISO to 1600 or 3200

What about noise reduction?
>>noise reduction Off,

Any other camera menu settings that I should change?
>>Set RAW/Fx button to astrotracer menu

Any tricks for "locking down" your lens focus once you have it? (I'm using manual lenses... trying the K 135mm f2.5 (at f4)

>>use photography tape or any tape to lock the focus ring after you have it .


my tips:
keep repeating the precise calibration until you get the good shot.
use a light pollution filter to combat light pollution.

best regards,
gleeman

[Stone G.]

Sorry for the question dump! Thanks for any replies. I hope to take another run at it tonight.

Some very good questions cheekygeek - and actually a good script for you to make your own tests and experiences, because hardly any astrophotographers - including astrotracer users - do things exactly in the same way and sequence. But here are some answers from my point of view, actually very much in line with gleeman's above:

1. How do you determine the proper exposure for your sub-exposures? Do you want the histogram spike to be just off the left edge?
Using histograms doen't make much sense to me. I shoot under skies where light pollution plays it's heavy hand. But I do use the LCD viewer a lot. If I can see my subject, if only just and barely, on top of the light pollution I know that I have captured some excess photons to work with.


Unprocessed image, DA* 200mm lens at f/3.5, 20 seconds and ISO 1600. Shot in late July under a very bright summer night sky.
Click on images to see larger versions.

2. Do you find that the menu is wildly over-optimistic in what it says your maximum time of exposure is possible?
That depends. There is obviously a significant difference in shooting a 5000 px wide image for un-cropped and downsized viewing on the web and then for shooting with tight, 100% "pixel-to-pixel" presentation in mind:


Uncropped stack of Hercules-M13 images. Same exposure details as above.


Non-resized 100% crop of the above. I.e.: Each pixel that you see matches one pixel on the sensor.

Obviously, you will have to establish your own limit as to acceptable drifts. My limit is usually around 4 pixel widths and in that case, I should say that stated maximum exposure times are overly optimistic. But I think the times shown assume "uncropped images for web-viewing".


3. I shoot in RAW+, is that OK?
That is perfectly OK. I do the same. raw-files have the obvious benefit that there are 12 or 14 bit levels for the stacking software to work with and thus, you should be able to get a better dynamic range in the final picure when that is needed.

4. Are you going to see results in the JPEGs or only after you have stretched the histogram in post-processing?
See also answer to Q1. above. You will never get near to an acceptable result without some serious post-processing but here's a small dirty trich, reference the image for Q1: Autostretch your levels. That will (normally) give you a clear indication of whether you have captured enough excess light to work with:


Same Image as 1 above. Levels stretched.

And then, finally:


Stacked, Post-Processed and Cropped final result.


5. Do you turn Auto-ISO off?
Yes, by all means! Your camera doesn't have a chance to guess, what scene you are shooting.

6. What about noise reduction?
You should turn all type of noise recuction off. BUT DON'T "CHEAT" and leave flat-frames and dark-frames out of your work-flow. You can stack without such frames, but results will usually be MUCH better if you do that extra effort.

7. Any other camera menu settings that I should change?
If you use JPEG-files, you should set white balance to Daylight and not Auto. I may also immodestly refer to my tutorial on camera settings for astrphotography here: Camera Settings for Astrophotography

8. Any tricks for "locking down" your lens focus once you have it? (I'm using manual lenses... trying the K 135mm f2.5 (at f4)
That's a VERY fine lens to start with. I would avoid using lenses with any tendency to focus creep (or zoom-creep, but I prefer not to use zoom lenses). However, my Tamron Adaptall-2 350mm mirror lens is exceedingly sensitive to proper focus, and here, I often use a small piece of tape to fix focus once I am confident, that my system is in thermal equilibrium. I establish focus and check it regularly using live view on a brigt star at maximum (8X or 10X) magnification.

- - - - - - - -
Whising you a lot of pleasure and fun under the stars!

[Stone G.]

my tips:
keep repeating the precise calibration until you get the good shot.
use a light pollution filter to combat light pollution.

Thanks gleeman - I can see that we both use the SMC DA* 200mm lens. Are you using light pollution filters for that - and if so, can you give more details. (I have made a small, primitive filterholder for the rear of the DA*200 and am actually contemplating getting myself a 1.25" LPR filter)

[gleeman]

Hello Stone,

yes , I use the IDAS LPS-P2 filter(for slight to medium light pollution ), so i can set the exposure up to ISO4000 F2.8 130sec so far... (W/ DA*200) under light-polluted skies.


attatch:
1. 77mm for DA*200
2. 48mm (modified to 43mm rear filter holder) for Tamron 300/2.8 adaptall

[gleeman]

hello all

l'm starting a Facebook astrotracer group
https://www.facebook.com/groups/556146854439260/

[Stone G.]

Finally a (single) clear night after an entire month with cloudy nights. Rather than trying to do something "usefull", I decided to try something silly and try out my Astrotracer with my SP 350mm f/5.6 Adaptall-2 lens and the SP F-series 2X teleconverter.

Now, a 700mm f/11 system isn't exactly the first choice for deep-sky photography, but i was merely interested to see how Astrotracer would cope with a 700mm focal length during some 15 seconds exposure.

So here are some results at ISO 3200, (click on images to see larger versions 1280 px wide):


Pleiades; 8 images stacked in Deep Sky Stacker, (non-cropped image)


Star Zeta Tauri; 6 images stacked in DSS, (non-cropped image)


Star Eta Orionis, Alnitak in Orion's Belt, 6 images stacked in DSS, (non-cropped image)



Orion's Sword with M42. I took 8 pictures each at 15, 10, 8, 4, 2 and 1 seconds and let DSS choose the (27) best for stacking.
Again a non-cropped image.

Now, this is certainly not "proof" that Astrotracer can easily handle focal lengths as long as 700mm at the moderately short exposure times of aboutr 15 seconds. But it does show, that the success rate in larger than zero.

[olveres]

Hi,

I have a K30 and the O-GPS1, and I am trying to experiment with it using old M42 lenses via an adaptor. When I use the astrotracer function, the F stop returns as "--", which I understand, but if I try to change the time of the exposure, it only goes so far as 60 seconds, occasionally it'll hit 1'20". The lenses I am trying to use are a Sigma 600mm f8 mirror lens and an old Soligor 400mm f5.6.

I put a 55-200mm DAL zoom on and at 200mm also had a similar issue, although naturally the F stop can now be changed. If I pull it back to 55mm the problem goes away.

If I use my 35mm f2.4 or 10-17mm fisheye I have no issues whatsoever.

Help?

[kypfer]

Hi,

I have a K30 and the O-GPS1, and I am trying to experiment with it using old M42 lenses via an adaptor. When I use the astrotracer function, the F stop returns as "--", which I understand, but if I try to change the time of the exposure, it only goes so far as 60 seconds, occasionally it'll hit 1'20". The lenses I am trying to use are a Sigma 600mm f8 mirror lens and an old Soligor 400mm f5.6.

I put a 55-200mm DAL zoom on and at 200mm also had a similar issue, although naturally the F stop can now be changed. If I pull it back to 55mm the problem goes away.

If I use my 35mm f2.4 or 10-17mm fisheye I have no issues whatsoever.

Help?

This is totally normal. The astrotracer function only has a limited amount of adjustment it can make before the stars "move too far". With a wide-angle lens up to five minutes can be expected, though, to a degree, acceptable results may depend on which part of the sky you are looking at ... the stars "move faster" at the celestial equator than they do around the poles.
With a long telephoto, as the field of view is inherently narrower, the camera can only adjust for a shorter period of time.
If you want to try to "cheat" things, tell the camera you're using a shorter lens, say 200mm instead of 600mm ... I think you'll find the trailing becomes somewhat excessive


Good luck

[olveres]

Hi,

I have a K30 and the O-GPS1, and I am trying to experiment with it using old M42 lenses via an adaptor. When I use the astrotracer function, the F stop returns as "--", which I understand, but if I try to change the time of the exposure, it only goes so far as 60 seconds, occasionally it'll hit 1'20". The lenses I am trying to use are a Sigma 600mm f8 mirror lens and an old Soligor 400mm f5.6.

I put a 55-200mm DAL zoom on and at 200mm also had a similar issue, although naturally the F stop can now be changed. If I pull it back to 55mm the problem goes away.

If I use my 35mm f2.4 or 10-17mm fisheye I have no issues whatsoever.

Help?

Ok, might have solved this myself. When I switch the camera on it asks me what length lens is attached. By basically just saying it's 50mm, regardless of what it actually is the problem seems to have gone away. I'll give it a whirl tonight.

[slartibartfast01]

Ok, might have solved this myself. When I switch the camera on it asks me what length lens is attached. By basically just saying it's 50mm, regardless of what it actually is the problem seems to have gone away. I'll give it a whirl tonight.

You will find that it won't track properly at all if you input the wrong focal length.