Balance on a SW Star Adventurer 2i & Flats Capture - Forums

Topic starter

Nov 14, 2021 · Edited: Nov 14, 2021

Hello everyone,

Recently I bought a SA and yesterday I was able to try it for the first time (w/ Nikon D5300).

My query is this :

In order to achieve better balance on my SA I need a lens collar i believe, but my lens is a vintage old lens(telear-n 3.5/200mm) and i cannot find something universal that will do the job...Is there anything like that around that I can buy in order to achieve balance on declination axis? In order to balance depending on the angle of the DSLR I had to slighlty move the counterweight, otherwise the mechanism always fell.

Or it is prefferable to mount my camera on a ballhead and then on to the SA (total weight around 1.3 kilos) or maybe should I try to achieve better balance with the L bracket and counterweight as is without the lens collar and there something I do very wrong?

Overall I maanged to captured some data, but @ 20secs exposure and the stars was not round at all.

Also I have another question about flats ,I went on and captured on my laptop screen on an even white wallpaper in manual mode , same aperture/focus and shutterspeed around 1/2000 in order for the histogram to be somewhere in the middle.Here is a sample, is this ok by flats standards (I have no idea)?

Thank you!

Nicholas Gialiris

Nov 14, 2021

Hi Dimitris,

I also have the Star Adventurer with my William Optics RedCat51 250mm APO and Canon T5i DSLR when travel imaging. First off, avoid a ballhead if at all possible as it will only create balance and flex headaches. Ideally mount camera/lens on the Fine Tuning Mounting Dec Assembly for a solid and efficient way.

Also keep the total payload on the SA to 50% (give or take) of the 11lbs recommended payload when imaging; too heavy and will cause tracking issues.

I balance using the counterweight and will actually use some heavy bolts (or other creative means) that slide nicely on the shaft and are secured if I need to add weight; you can also buy additional counterweights.

I take 120s - 180s lights without star trails; of course, you have to polar align as well as possible; fiddly with the SA but just takes patience, and ideally with everything mounted so the PA stays; if you add camera/lens afterwards, will shift the alignment.

Your flats do look as expected; grey image that when stacked and processed will remove the dust bunnies, optical abberations, junk on the camera sensor and lens train; this takes some practice to find the optimal exposure and light source.

Hope it helps.

Helpful Engaging Supportive

Dimitris Kavallieratos

Topic starter

Nov 14, 2021

Nicholas Gialiris:
Hi Dimitris,

I also have the Star Adventurer with my William Optics RedCat51 250mm APO and Canon T5i DSLR when travel imaging. First off, avoid a ballhead if at all possible as it will only create balance and flex headaches. Ideally mount camera/lens on the Fine Tuning Mounting Dec Assembly for a solid and efficient way.

Also keep the total payload on the SA to 50% (give or take) of the 11lbs recommended payload when imaging; too heavy and will cause tracking issues.

I balance using the counterweight and will actually use some heavy bolts (or other creative means) that slide nicely on the shaft and are secured if I need to add weight; you can also buy additional counterweights.

I take 120s - 180s lights without star trails; of course, you have to polar align as well as possible; fiddly with the SA but just takes patience, and ideally with everything mounted so the PA stays; if you add camera/lens afterwards, will shift the alignment.

Your flats do look as expected; grey image that when stacked and processed will remove the dust bunnies, optical abberations, junk on the camera sensor and lens train; this takes some practice to find the optimal exposure and light source.

Hope it helps.

Hi Nikola,

It needs patience & much practise indeed, next time I will be more attentive to every detail . So I guess no tool can be found as an universal lens collar, so I will try to balance out my setup the best way possible.

Glad my flats seem ok!

Thank you

Nicholas Gialiris

Nov 14, 2021

Yes indeed, its all in the little details!

@Thibault, like I was saying to Dimitris, a common issue with trackers like the Star Adventurer, iOptron Sky Guider etc., is the payload capacity you put on these "little" mounts.

The SA has a max payload of 11lbs; in astrophotography, just like with heavy-duty EQ mounts, the recommendation is to keep the payload to about 50% of the recommended spec; not that you can't go higher, especially when just viewing objects, but when imaging, pushing the motor/gear assembly beyond a certain amount will start to adversely affect the ability for it to track accurately in RA, due to sagging, flexure, off-balance etc, making it hard to shoot above 30 sec; you can start adding a guide scope, guide camera, PHD2 guide software to guide in one axis only (RA) but that makes things even more complex and heavy!

My WO RedCat51 at 250mm with Canon T5i achieves a nice balance without "tipping the scales"; using heavier long focal length lenses starts to put a bigger load, making tracking more difficult; you have such an issue with 60/360.

As a test, if you put the camera/lens and counterweight shaft parallel to the ground with the counterweight plate right at the extreme end and let go (gently) and the camera/lens swings down hard, you are overweight (no ballheads BTW! Even worse issue).

As well, don't disregard Polar Alignment; just like with EQ mounts, the higher the accuracy you achieve the longer the subs you can take, with the balance factor of course affecting it.

SA can get you 60-180s exposures; 1-2 minutes is the "sweet spot"; I get 3 minutes because I carefully balance, don't over-exceed the payload and carefully do Polar Alignment with everything mounted so no shifting after locking things down.

Cheers.

Helpful

dkamen

Nov 14, 2021

Hi Dimitris,

About flats, when we say "the peak of the histogram must be in the middle" we actually mean the histogram of the linear data. That is, the average value of a pixel in the raw file must be about 30-35 thousand (65,535 being the maximum). The camera does not display the linear histogram of the raw data but the stretched histogram of the JPEG preview which is typically significantly shifted to the right. So even though you in-camera histogram is in the middle, the actual raw histogram is in fact very close to the left side of the x-axis.

Long story short, aim for an in-camera histogram about 4/5ths to the right and you'll be fine. Don't worry if it looks too bright, as long as it is not completely white. Still, I don't think actually hitting the middle of the histogram is actually carved in stone. I think anything bright enough to make read and thermal noise a non-issue but not bright enough to actually have blown out pixels is okay. This can be as little as 5,000 ADUs.

Also, 1/2000 is a bit too short when the source is an LCD. Aim for at least half a second. Dim the LCD as much as possible (the surface will look almost black to your eye) and if it still isn't dim enough put a printer paper or two in front of it.

Of course the final test for a master flat is whether it corrects your dust motes and vingetting or not. Flats can be surprisingly difficult to get right with lenses due to various reflections. I am currently re-calibrating several thousand subs because I discovered my flats work a million times better if I take them with the lens hood removed, due to reflections on the inside of the hood.

About your tracking problem, I don't think DEC imbalance is so important for SA, provided it is not pathological. DEC balance is important when you are guiding in DEC which the SA doesn't, or perhaps when you are imaging too low on any horizon. As the other said, RA balance and polar alignment are extremely more important. But one thing I guarantee is a ballhead will make things much, much worse.

A final note: you can do amazing stuff with 20 second exposures at 200mm f/4.5 (I am assuming your lens needs some stopping down from 3.5). Just make sure you use an ISO that is high enough for your in-camera histogram to not clip to the left. Typically for Nikon cameras in a suburban setting this is ISO400-1250.

Cheers,
(also) Dimitris

Helpful Respectful Engaging Supportive

Dimitris Kavallieratos

Topic starter

Nov 15, 2021

Hi Dimitris,

About flats, when we say "the peak of the histogram must be in the middle" we actually mean the histogram of the linear data. That is, the average value of a pixel in the raw file must be about 30-35 thousand (65,535 being the maximum). The camera does not display the linear histogram of the raw data but the stretched histogram of the JPEG preview which is typically significantly shifted to the right. So even though you in-camera histogram is in the middle, the actual raw histogram is in fact very close to the left side of the x-axis.

Long story short, aim for an in-camera histogram about 4/5ths to the right and you'll be fine. Don't worry if it looks too bright, as long as it is not completely white. Still, I don't think actually hitting the middle of the histogram is actually carved in stone. I think anything bright enough to make read and thermal noise a non-issue but not bright enough to actually have blown out pixels is okay. This can be as little as 5,000 ADUs.

Also, 1/2000 is a bit too short when the source is an LCD. Aim for at least half a second. Dim the LCD as much as possible (the surface will look almost black to your eye) and if it still isn't dim enough put a printer paper or two in front of it.

Of course the final test for a master flat is whether it corrects your dust motes and vingetting or not. Flats can be surprisingly difficult to get right with lenses due to various reflections. I am currently re-calibrating several thousand subs because I discovered my flats work a million times better if I take them with the lens hood removed, due to reflections on the inside of the hood.

About your tracking problem, I don't think DEC imbalance is so important for SA, provided it is not pathological. DEC balance is important when you are guiding in DEC which the SA doesn't, or perhaps when you are imaging too low on any horizon. As the other said, RA balance and polar alignment are extremely more important. But one thing I guarantee is a ballhead will make things much, much worse.

A final note: you can do amazing stuff with 20 second exposures at 200mm f/4.5 (I am assuming your lens needs some stopping down from 3.5). Just make sure you use an ISO that is high enough for your in-camera histogram to not clip to the left. Typically for Nikon cameras in a suburban setting this is ISO400-1250.

Cheers,
(also) Dimitris

Hi Dimitris,

Thanks for the advice, I am sticking to balancing with a counterweight then . Another question ,is it worth to purchase a clip in LP filter for my Nikon D5300 or should I invest in it after I get some experience? I will be mainly imaging from bortle 8 (Athens) so LP is a major issue.

I am right now at the crossroads of buying PI license or investing in a clip-in LP filter...

Nicholas Gialiris

Nov 15, 2021

Highly recommend LP or UHC clip filter for your Nikon; I image from Bortle 8 as well and use Broadband and Narrowband filters all the time to battle the heavy light pollution; worth the investment.

Dimitris Kavallieratos

Topic starter

Nov 15, 2021

Nicholas Gialiris:
Highly recommend LP or UHC clip filter for your Nikon; I image from Bortle 8 as well and use Broadband and Narrowband filters all the time to battle the heavy light pollution; worth the investment.

Do you have any specific recommendations ? I own a D5300…

Thanks.

dkamen

Nov 15, 2021

I don't know, NB imaging is a different story but LP for broadband, I just don't think it makes much difference compared to imaging without it and subtracting light pollution (Astropixel Processor and Start Tools have *very* sophisticated routines for that) while it does have a tendency to ruin the colours and definitely introduces complications with flats and reflections, especially if it is a cheap one. Most of my images are also from Athens, bortle 8-ish (eastern suburbs) and I have never used an LP filter.

andrea tasselli

Frequent contributor

Nov 15, 2021 · Edited: Nov 15, 2021

Do you have any specific recommendations ? I own a D5300…

There are NO clip-on filters for APS-C Nikons. Not even IR cut. With a lens of your aperture I'd probably guess a 48mm filter in front isn't a lot of aperture loss so you'll be probably want either a Baader Semi-APO or a Optalong L-Pro for broadband work. Both will cut nicely across a lot of light pollution (at the price of some transmittance loss , as all filters do). Narrowband is another story and I would NOT recommend you go down that route until you get better at setting up, tracking and processing.

Helpful Concise

watcher

Nov 16, 2021

You don't need a collar to balance your lens /camera combo. Use your camera tripod threaded hole and get a rail to mount to the camera. with most of the rail forward of the camera you can find a nice balance with the combo. This is OK unless the lens is very heavy.

Good luck

Concise

Dimitris Kavallieratos

Topic starter

Nov 16, 2021 · Edited: Nov 17, 2021

Thanks for the replies! I am going to proceed with my current equipment and build up some experience.

Does anyone have any recommandation for a hot shoe adapter for my Nikon in order to mount a red dot finder (I have this red dot finder from my telescope SKywatcher Star Discovery 150p goto)? I can't seem to find a good match online...

andrea tasselli

Frequent contributor

Nov 16, 2021

Does anyone have any recommandation for a hot shoe adapter for my Nikon in order to mount a red dot finder (I have this red dot finder from my telescope SKywatcher Star Discovery 150p goto)? I can seem to find a good match online...

I have the same on my D5100. Here is what you need:

https://www.ebay.co.uk/itm/331768579838?_trkparms=ispr%3D1&hash=item4d3ef2c6fe:g:S7IAAOSwnLdWsKbv&amdata=enc%3AAQAGAAACkPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSprd4IgPv6LBzlteBBg9Pexsx5Zt8ykz2uGmFl2SjDMWzL4P6OEaNcdLfF7Y8e9YvPkwaTWJHJhcNF4ACEr%252FKasDFZx0l76wJzB5Alx2bGD93coFY%252F5Uf%252Fas3Qe6tx0WgHUV2eS5RKrYlH6mUz7hUM9OdYqM7vIFAX%252FTPvW8Sxom9ILUsP6uohHKT62Coujq8fiQE1u%252F9C1w5iEJp5rOE97LhK6GqfaM9laU%252F4c%252BGvb%252FZw5QsTuW5KiTu2IiT0S%252FAUa%252BBe1SaBKOh7CrfnYV7zRcfbXRnXbrpsihi0rvwL7Qj%252FDljuR8lmnVmVllzwr6j%252B773LsJtN%252BH5PJKUh%252B55VAAF4rWQgnpsjVYU%252FE%252BkuxCXecXUQ%252FQ0KOvnMLQ1PRUjz1okWEu1IB3anOH88o5r1buibM1CV41aA%252Fn0iOrs0fQX99MgmClVf2cZ9UQ1wSlbiAzGMto6ajGAuecsMi4Ry7MA%252FApczqknW2Es2E%252BeemiEw1OCe%252B93ct4S6yYb%252B1sSM1Av1FiMMAMFGFqbeIGarDnUPVkfB%252BdBnyXzIqmsVfYD2AF%252FvCQKxhsrfUjv3y3Y3jb%252B2wSZQKwUuC3kaRnJHweGEkRYpCMPuie%252ByENt%252BM9yxt%252FcnymiF3Su5Bi4rduMZ5GEZf2yqMouDpfVA3fPKwq2%252F5itcUWJVs56JEKUvFt4b1m%252Be5A4%252F4n7JQPpIr9XLv%252FbPa64dkX7JbEF%252BUFRyW5%252BuC7sdH6CUtEA9dwm5cgLT2u6y9%252BLKcvwDKEkYV%252Bl%252BZe%252F%252FOJBtsZzyu73JDzymI56iUDc5XzweUcAQZfdPPXR8uiJi9UsQESWqIiSat1E%7Cclp%3A2334524%7Ctkp%3ABFBMgKyuiKVf

and:

https://www.ebay.co.uk/itm/174928878461?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649