bomberbaz

This isn't really a question but I needed a catchy title as I believe there will always be people who, at least at some point try to bypass the benefits that are to be achieved by travelling from an urban or semi rural area to a true dark site. I should know this as I was one of these people when I first got into astronomy circa 10 years since.

So unless you are one of the lucky few who live in places such as Brecon beacons, Forrest of Galloway or similar, please read on.

When I first got into the hobby, I read countless pages on forums and was constantly drawn towards XXmanufacturerXX super duper filter in an effort to get amazing results from my back garden with an SQM of 17.5/Bortle 6 and despite numerous people telling me, I was at first unable to grasp the idea that a few quid on petrol was my best option instead of some fancy filter. Part of it was at least due to lack of confidence as I had not done this before.

Anyway, I did start travelling out to darker areas after a few years when I joined a local group of amateurs like myself who had meet ups at semi dark places down to around bortle 4. Still not mega dark but certainly much better than my back garden and I did notice an improvement in my results. I think the impetus of actually joining a group gave me the little push and boost in confidence needed to get me out and from then on I did look more and more for darker places to view from. 

My epiphany came around 5 years ago when I went to Galloway Astronomy Centre for a weekend.  I won't walk you through every last bit, simply that I had to ask where stars were to align on because I was lost in the sea of light which greeted my eyes when I walked out for the evening session. I saw as much in one night under those gorgeous skies than I had seen in the previous 4 years at numerous other sites.

It was at this point, with the sound of a huge penny clanging around in my head that I became committed to travelling for my dark sky viewing. Sadly some of my previously great sites have lost some of their lustre since the UK's obsession with LED street lighting. These lights may be energy efficient but they are also dark skies worst enemy. Slight tangent here but my most previous visit to Galloway AC showed the sky had brightened from SQM 21.5 to 20.5. Clouds previously invisible were able to be seen, worrying times. 

Back to the thread,  I will say to anyone who has a car and doubts if the travel is worth it, try it. Even if you have a 1 hour or more drive the results will more than be worth the washed out view from a light polluted garden. If you are struggling with travel, join an astronomy club and I am sure someone will oblige in taking you to a star party.  

This is said on here time and again but it is so important a point I shall repeat it. You will see more through a 4" scope at a good dark site than you will through an 8" one in a light polluted area. 

I now have three dark sites at varying distance. One is a half hour and sqm 19.5, great for impromptu or short sessions but I would say it only just qualifies as dark. There is one an hour away and sqm 20 ish although it is very exposed but my local group use it so I do with them. My final one which I have visited but as yet not viewed from it or light unmeasured. This is 1.5 hours away and I anticipate it will be SQM 21+ or bortle 2 going off my findings to date. I have high hopes for this one.

My most recent report on here was from a site with sqm 21+ skies during which I achieved a galaxy down to 14.2 magnitude and views of other objects that were amazing and simply not achievable in an urban environment. This was actually in Galloway but a few miles travel from the astronomy centre and a well placed hill did wonders for the sky.

So get to the darkest place you can even if it means going that extra few miles on the road. You will see and remember more from one great night in pitch black than you will from ten average nights under LP'd or semi decent skies.

Happy viewing all. 

Steve

12 hours ago, Ships and Stars said:

Great report, M51 is wonderful when conditions play along. 14.2 mag is getting seriously faint in my book, and will have to try for a quasar sometime, have never seen one!

14.2 was the faintest possible smudge you can imagine, I blinked it into view. It was NGC 3357 which is elliptical and appears to have a very bright core NGC 3357  It is this core which helped it stand out no doubt. 

One of the great things about my setup is the scopes DSC, it is incredibly accurate, to within 1/8 of a degree this night so really does help confirm your target object.

Ref: quasars, they really are nothing to view but it's a bit like the horsehead, we go for it because it's there. Incidentally it was 3C 273 which has reported range of 1.5 to 2 BLYears, I obviously went for the furthest. 👍😁

And your spot on about M51, it was exquisite. There are not enough adjectives to describe how beautiful it was last Sunday. It will be on my hitlist for sure next time I get out.

On my way down to my stargazing spot last night(sunday)I saw this along with it's mate. Good omen

Actually it was difficult as you can see from the other picture the sky is full of crud (from saturday).

H-head was a maybe seen, can't  say it was a definate.
Highlights were getting down to mag 14.2 galaxy (470mly away), a quasar in virgo (circa 2 billion ly), sirius b (the pup, unconfirmed) and M51 the most detailed view i ever have had. Distinct swirl, highly detailed  structure of the merging pair and the bridge clearly visible. The main galaxy detail was almost jumping out at x170, stunning.

Best bag, the quasar, best view, M51. I never thought such detail was possible visually. 

Hoping Friday might offer up a focussed but short session. Trying to keep swmbo happy too. 

On 28/03/2022 at 15:31, LaurenceT said:

It arrived today and it's a perfect fit, long enough to get balance on my mount and also room to add my Asiair Pro and TP-Link mini router 👍 Thanks again for the suggestion. I now have to spend another £40 odd to get the ZWO clamp😅.

No worries pal, glad it works

@vlaiv just found this off the manual for a ASI183

ASI183 Manual EN.pdf (astronomy-imaging-camera.com)

"ASI cameras are designed to have very low power consumption which is around 300ma@5V"

I don't think power is going to be an issue.

Cheers for the help.

Steve

14 hours ago, vlaiv said:

If uncooled camera will work on USB 2.0 port - then it draws max 0.5A on 5V. If it can work only on USB 3.0 - then it draws max 0.9A at 5V.

As for ZWO computer - look at the specs on their website:

They recommend (quite wide range) 2-5A at 12V

This is probably due to 12V ports that it provides - maybe base consumption is 2A at 12V and other 3A are for these additional ports?

Thanks vlaiv, good point about the variable power for ZWO plus the USB 3.

Assuming the maximum load of the two camera and cooling mod I get 4.1A.

The ZWO raspberry will also draw something and there is a very small draw for the mount so will work on assumption of 5A for all components. 

If the cooling mod is drawing too much power for the computer AIR I could bypass it and go direct to power supply but going via the AIR makes it far tidier. 

cheers

steve

2 minutes ago, AstroNebulee said:

It does sound like an improvement indeed for some reason. Maybe the mount needed a bit to hone itself in, the seeing or transparency got better or wind dropped calibration could be any number of things, I'm pleased it's settling and you'll see a big difference with dithering, can't wait to see your results. You're doing great Steve 👍😊

Cheers Lee. On a side note my cooling mod is doing as expected at about 15F below ambient, however the problem I am encountering is related to the powering of the mod. So I am getting a 2.1/5/.5 jack to fit into the AIR to draw power directly from a powertank and not give out after an hour which is what is happening with the current bank of lithium AAA's.

I am going to stop with an hours data of M81, see how that works out with the latest tranche of alterations. All good fun.

Steve

Second update, tracking actually appears to have tightened up since I introduced dithering into the imaging process. No idea why it appears better but it definitely is improved.

As per previous post for now I am not going to try figuring anything out but it is a nice thing to get.

@AstroNebulee I am dithering every even number sub (2,4,6 etc) just to see if this helps improve results. I am using medium setting on gain which is 111 (unity) and currently halfway through 40 x 2 minute exposures. Lets see what this gives me on M82

Ok so tried your settings Lee and my guiding went completely to the dogs, obviously something wasn't right somewhere with what I was doing.

Anyway I have reset everything and will run with average guiding for now and concentrate on getting my exposure/gain settings right as well as flats/darks/bias capture before I tinker further.

Think I am trying to move to fast so for now I am gonna stick with basics.

Hello, I am trying to figure out whether I need a bigger power supply now as I have more kit being attached to it. Currently using an old power tank battery which long since lost it's external case but I am considering a lithium alternative.

As well as the camera, mount and Air, I have a peltier cooling mod which I know draws 2.3 aH, the rest I am trying to figure.

So does anybody know how much power uncooled zwo cameras draw and also the AIR Plus?

I believe the AZ GTi mount draw is next to nothing so I am not really concerned about that.

TIA

Steve

13 hours ago, ONIKKINEN said:

Is that a DIY cooler? Looks interesting.

If you can make the DIY cooler work at consistent temperatures night after night, you can take one set of darks, biases and dark flats and use those for every session and dont need to take them each night. If your flats exposure time is very short you can get away with not using dark flats and instead just use bias to calibrate the flats. If its maybe not so controllable you could take several sets of calibration frames at different temperatures and then use whichever set is closest to the actual imaging temperature that night. Flats will have to be taken in the exact condition the optics were in when imaging, so before you remove the camera from the scope and each night with their own flats. If you can leave the setup as is each night and dont take anything apart, its possible your flats will work just fine reused but i would take them every time. Using a light panel of some kind is the simplest method, but since you have 50mm of aperture you can use a decent sized phone screen, tablet or laptop screen as a light source for the flats. and so probably dont need an extra tool for this. Very quick to take and so not much in the way of excuses to not do this each time you're out.

As for the multi session thing, you need to calibrate your session with matching calibration frames. So if you can take a library of darks, bias (and dark flats, if bothered) at matching temperatures where they can be reused indefinitely, the only calibration frame that is session sensitive would be the flats. Once you have calibrated the subs well it doesn't matter from which session it was anymore and you can stack any number of them together without issue and disregarding the session it was from. If you dont want to go through the trouble of storing calibrated frames you can use DeepSkyStacker with the "groups" function to drop each session to their own group. This feature calibrates each set with their own calibration frames and then stacks everything together in the end.

Some good information here and pretty much along the lines as I had been thinking.

First my DIY cooler you spotted, it takes temperature down by roughly 15 degree C to the ambient. I purposely made the cooler to not be to efficient so as to avoid condensation on the sensor. (This has been known with other ones which overcool the sensor. Apparently dedicated cooled ZWO cameras have a mini heater tape near too the sensor)

Anyway I could in theory make a library of darks using 2 degree increments for example. 

I keep my camera screwed to the scope, however like you alluded to I took a white screen "screen shot" on my phone and used this to cover the aperture last time for my flats so its really not a biggy, it is the darks above which are the biggest pain as far as I am concerned so a library I shall collate.

Thanks very much for the help.

Steve

Very new  to imaging. Using a very simple rig to play around, see below.

Question is, if I take data from same object over several nights, what do i do about flats and darks plus bias. 

Do I do all at end of each session or one job lot at my overall end of data capture.

cheers

steve

duplicate

Yes noticed a few variations on my guiding rates and/or settings there Lee, I shall be making changes (when conditions allow) to my own settings and see if my tracking improves.

I should point out that until last week I had never even seen a guided setup, so the fact I am actually managing to do it at all still amazes me 😂

Steve

26 minutes ago, Varavall said:

Hi

Try this one https://pbleic.medium.com/star-reduction-in-gimp-a-tutorial-using-wave-decomposition-59d209e53bc6

There are a couple of errors in the steps. Step 13 to clear the "dancing ants" got to menu, select, none; and in Step 15 highlight the original visible layer that is below the mask layer to effect erode.

Hope that is some help.

I will give it a try, thanks for the info.

26 minutes ago, AstroNebulee said:

It's still guiding well on the multistar guiding and picked out around 10 or so stars to guide on plus the main one.

You could always try a lower gain on yours and see how many stars it picks up. With your gain at 250 are the stars quite bloated? 

This screenshot is from a few weeks ago and before I refocused my guidescope so the stars are a little off and the hfd of the star a bit high but this is with gain 60. Note only using one star to guide in the screenshot but using multistar now. The guidestar in the box in top left should have the red graph bit at a point and not flattened off. 

Cheers 

 

Lee 

 

 

You have just made me think, I actually altered the focus last night when moving the system around and forgot to check focus again later before using the kit.

Anyway, I will drop my gain and recheck focus before my next run to see if that helps. Looking outside that is unlikely to be tonight though, lol.

Steve

2 hours ago, AstroNebulee said:

Ahh sorry Steve (I'm a bit thick anyway haha) No I'm using my zwo asi120mc-s for guiding on the zwo 30mm f4 guidescope. My gain is around 60 and exposures are 2 secs. Though my gain can range from 50-70 depending on the quality of the sky. 

Cheers 

Lee 

Interesting gain, I am using around 250. Wonder if there are too many stars that is affecting tracking accuracy as a result of this.

Are you still managing multi star tracking easily enough Lee?

Cheers, steve

3 minutes ago, AstroNebulee said:

Thank you, though my guiding was more generally around 1"  but kept lowering to that value, so well happy. 

With my zwo 294mc pro I was using 120 gain which is the unity and 180 sec subs. 

Sorry should have been specific, I  meant on your guide camera. I am assuming your not using a pro camera for guiding.

I am looking at purchasing a powertank for my mini imaging rig.

Power draw will be based upon 2 x ZWO uncooled camera's, a SW AZ GTi mount, ZWO ASI Air plus and a peltier cooling mod which draws 2.25amps.

To date I have only looked at the SW powertank 17aH and the Celestron lithium powertank pro 13.2aH.

I don't [removed word] to lug a leisure battery around so I am not going down that route.

Interested what others use as their "in the field" power provision and why.

cheers

steve

11 hours ago, AstroNebulee said:

Just got in from grabbing 2 hours worth of data on M101 tonight, so pleased to be back out under a moonless, windless, clear night sky even if the transparency was rubbish. Couldnt really make Virgo out atall and Leo was washy. 

And quick couple of screenshots, guiding was very good too using multistar guiding. 

Hoping to grab more data on it moro night if it stays clear. 

 

excellent guiding that pal, what exposure and gain you using?

24 minutes ago, AstroNebulee said:

165 gain could be good it's all about experimenting, I wish I could image the monkey head but after meridian no good, look forward to seeing your results 👍

Just a quick FYI is the data I captured has dust motes on it and as I forgot to get flats it might be for deleting. Not sure if it is rescuable as i am still a little unsure about the capturing of flats. Fine with darks and bias 

3 minutes ago, AstroNebulee said:

Just on having a quick look people say the unity gain is 111 for the zwo 183mc and some using 180 sec subs. You coukd always try 111 gain at 60,120 and 180 secs subs. 

I have aactually just done some subs of the monkey head neb at 60,120 & 180 although I have used a little more gain at average 165 so maybe overcooking it. 

I shall see upon my results. 

1 minute ago, AstroNebulee said:

On e you got the hang of it it's definitely worth dithering, makes a huge difference to the subs. I know my set up is different scope and camera but my 294MC pro I use gain 120 and normally do 180 sec subs and dither between each one. I haven't tried longer subs yet as I find a good balance in guiding and images with 180secs. 

I'm sure on the charts for your camera it will have an optimal gain to use. 

I'll have a look. 

I am using the 183 uncooled although I have the cooling mod installed. TBF my batteries died earlier 🤣

3 minutes ago, AstroNebulee said:

The guiding can vary from mount to mount and depending seeing, transparency, wind and mechanics of the mount. Mine will guide admirably under 2 " generally and can get as low as 0.7" at times from North to south then if I try to guide after the Meridian all hell breaks lose and throws a strop. The mount does perform very well considering its really an alt az mount in EQ mode and not intended for AP. 

Worth looking in your guide log in the asiair when you upload images to laptop, it's quite interesting to see how the guiding went. 

Do you dither too? 

No I don't dither, still trying to get a hang of grabbing data first. TBH I have no idea how long my exposures should be, the gain I should be using so just playing about as yet. 

Any tips on exp and gain?

30 minutes ago, AstroNebulee said:

It's all great experience and it's a cracking image for the evoguide. I'm still quite blown away by the versatility of it. What is your guidecam and scope? Ignore that I can see it now I zoomed in on the guidecamera doh! How ate you finding the guiding of your set up, any issues? 

Just looking at it now and total error is running at a tad over 4 whatever that means, hahaha. 

The guidescope is an astro essentials 30mm. I have nothing to compare it too but using the 224 and multi star guiding it seems perfect to my eyes.