Quality of Star Adventurer

Hi Marcus and Karol,

thanks for your replies!

Marcus noted that my pollution filter eats 50% of the light. Well, without it the Pleiades would have been impossible to catch in Regensburg .
Due to the pollution I reduce exposure time to 3min otherwise the pollution takes over.

My Canon 600D is really noisy, so I even reduced to ISO 400, what is a pitty. Gottfried Meissner (https://www.astrobin.com/users/Gottfried/) uses a Fujifilm X-A1 which has a fantastic noise level! Maybe I move to Fujifilm, too.

Finally, the lens: I had a copy of Canon 70-200 F4, and it was simply awesome. Than I sold it and bought a Canon 200 F2,8. Now I have to stop down to F4 to get good images. Uah!  Maybe the Samyang is another option!

Doesn't stopping down with a mask reduce resolution ? With 72mm resolution is ~ 138/72 ~ 2" which is already half of a pixel.

And: How do you do focussing ?
Back to SA:
Without guiding SA is painful. I made M27 with 200mm but I had drop 50% of the images (http://www.hedenus.de/astro/2016-09-03-M27.png). With guiding I can make 5min frames without noticable error increase.

I wonder if all SA have the same error of if there is a quality variance.
I measured it as follows:
(1) Setting up SA carefully
(2) Short exposure (1/10s) photos taken from a star near the equator with a period of 10s
(3) Using Irfanview batch feature to crop a fixed region of the RAWs and store them as a series of PNGs. This region of ~100x100 pixels contains only the observed bright star.
(4) Write a program to find the moment of the images (intensity distribution)
(5) Make statistics for the coordinates of the moment over time
(6) Plot with Excel

Hi everyone,
I bought the SA last year and I'm absolutely convinced. I am using a Canon EOS 20d modified and for the moment a Canon Zoomlens EF-S 55-250 mm f/4-5.6 IS and with a focal length of 250 mm exposure times round about 600 seconds were no problem. Polar alignment is really easy and it takes me maybe 5 minutes to get the setup ready for use. I am living in Brunswick and for making photos I drive round about 50 km up to the Hochharz National Park where light pollution is no problem. So the SA is a wonderful portable mount for making long exposure images wherever you want. I think focal length up to 500 mm should be no problem but of cause exposure time than getting more important. I am planing to by a Takahashi FS-60 in the middle of the year so than I'll see what is possible.
By the way, if anyone got some got some experience with the Takahashi please send me your opinion.

Hi Harald,

recently I bought a Bahtinov-Mask und TS Telefokus (http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3285_Mikrofokussierer-mit-Fixierung-fuer-Kamera-Objektive-bis-D---80mm.html) (it is not so clumsy as it looks in the picture) which works very fine. First I use the live view then I make a 5s-10s frame an check the diffraction figure. The focus can be moved very smoothly and then it stays fixed! I tried various focusing methods but this works best for me.

I noticed that the Canon 200 f2,8 has chromatic failure which produces red rings  around the stars. When the ring appears, the focus point is found!

For focusing I look for an object very far away by daylight, preferably a tree. I focus on the crown until the branches getting sharp. I mark that point in red color between zoom ring and  focusing ring. Before starting a session I make a picture with these settings, get the cf-card out of the camera and in the card-reader for my laptop. Than zoom in the picture for checking the focus. It is only a tiny movement mostly to the right until the focus is perfect. Mark that point in green color and ready for take off
But as I already said, with the zoom lens I used increasing aperture for focal length higher than 180 mm is necessary.

Hi everyone, it's nice to find a friendly, knowledgable group. I am looking for advice/diagnosis help with SA -

I am new to tracking, having bought an SA in September, though I have a lot of tripod experience.
I am reasonably careful with alignment, and I have become more diligent at eliminating slack in the mount; I now regularly tension down the tripod with a bungee cord to my 12V-battery.

Still, at 200mm with 1.6 APS-C factor, 50 of 60 exposures of 30s long are rejected by ImagesPlus grading routine.

From what I have read above, I am suspecting that Periodic Error is the likely reason. i.e. that those 10 "bad" exposures are during the greatest PE shift. Would I be right as well that the gradual drift during 1 hour accounts for the 50 pixels shift that ImagesPlus reports after the translation routine?

I know there are 10 things that I could improve on, but would appreciate your advice on what the most important ones are. As someone else has said "alignment is not your biggest problem", a very practical approach to error reduction - there is no sense fixing the 2% errors when a 10% error is happening.

Your thoughts are appreciated.
Alister.

Bahtinov all the way! I also use DSLRcontroller (connected by wire) so I can use a loupe to focus on the smartphone image. Tiny adjustments to focus are possible without touching the camera, so no vibration, AND I can focus at -20C with gloves on using a smartphone "pen" to touch the focus controls:
https://sites.google.com/site/alistargazing/articles/focus-with-a-bahtinov-mask
One of the best uses of $10 ever.
Regards,
Alister.

Hi Franz,

I used the Star Adventurer as my only mount for my first year in Astrophotography, a lot of the time guided. I use a ZWO mini guide scope and a ZWO ASI 120mono mini guide cam. This setup is light, sometimes comes as an inexpensive bundle offer and would also be great fit for your setup. If your polar alignment is good, 5min exposures should be possible without issues on your setup.

Guiding is done via ST4 and PHD Guiding 2. Setup is very straightforward, install the camera drivers and PHD2, chose "on camera" as your mount in the setup wizard and just remember to put the "dec guiding mode" to "off" in the algorithms tab of the advanced settings, otherwise calibration will fail as the program attempts to calibrate the dec guiding.

Autoguiding would also be an option if you don't like to use a laptop for guiding, but I don't have any experience with that. I have only read and heard that the lacerta mgen2 works well with the star adventurer.

About the polar reticule illuminator: Maybe your battery is flat. Usually, when the battery is fresh, I have to turn down the intensity on the little dial because it is too bright. But once the battery gets old (or you forget to turn it off properly and let it shine for days like I managed to do ) the intensity starts to fade.

Clear skies, Marc

Hi Franz, I sent my mount to the factory to be assessed. Have yet to hear back. I had to limit my exposures to 60s at 100mm otherwise like you I was throwing away 50% of my subs. Also my mount would not calibrate with PHD2. I think mine is simply a lemon because others seem to be ok.
Al.

You can check if it is periodic error by plotting the star eccentricity against time. Many programs automatically calculate star eccentricity.
Mine showed no relationship. My shots with the roundest stars showed up randomly, even got good shots after an  hour.

Thanks for this link. A friend who I have been helping with their Star Adventurer gets nice stars at 250mm on a cropped sensor at 60s, no guiding. I would be happy with that. I am eager to hear what the company does with my unit.

Thanks for this link. A friend who I have been helping with their Star Adventurer gets nice stars at 250mm on a cropped sensor at 60s, no guiding. I would be happy with that. I am eager to hear what the company does with my unit.

Dont get me wrong, i also get nice round stars at 250mm focal length with my crop sensor at 70s but only on ~60-70% of subs. And those subs are randomly distributed within the bunch . maybe we are just expecting too much from the little SA.