coatesg

Absolutely! It took a fair bit of browsing around ephemerides to find an EB with a predicted eclipse at the right time (why are they always at the wrong time?! 🤷‍♂️). Luck has it that the last observation in AAVSO for this star was about 2 yrs ago as well, 4 yrs in Lichtenecker.

Yes CTB1. And the RA is pretty much bang on the zero line (good for triggering errors/bugs in software/mounts!)

Taking advantage of a clear evening! It's absolutely wazzing down tonight like it seemingly has been since Oct... It's the first time I've used Minima - it's fairly easy to use from first looks (though how much to rely on the error calcs, I'm not sure!). I had tried Peranso (which has much more functionality) before on a trial install, but I do relatively little EB work and so the $49 cost seemed a bit excessive...

Looks like a parfocalising ring? Or something to easily set a focus point?

Quite a productive evening before the cloud thickened (before the deluge today...). Two HADS light curves: These both contribute to the ongoing HADS study @Dave Smith and I (and others!) submit data for. FS CMi: period of 1.14hrs so quite quick this one. V447 UMa - another one varying by 0.5 mag over the space of 1.7hrs. I do wonder if this is multiperiodic given the smaller magnitude (brighter) in the second maximum compared to the first? Eclipsing Binary LM Boo (EW type) : AAVSO has period as 7.8702hrs. I used the "minima" software to analyse the curve and pinned the minimum down to HJD 2458907.5255 +/-0.0001. Have submitted this to hopefully be published in the JAAVSO in their eclipsing binary minima roundup. The minimum is quite a way off the ephemeris on the AAVSO VSX record - the last observation in the Lichtenknecker Eclipsing binary database is from 2016 and is similar in O-C. Data went a bit haywire at the end due to cloud. To check the calculated minimum plot the curve forwards and backwards around the ToM - should be pretty much coincident either side:

I think U Leo is a very ambitious project to have a go at for most observers! I might have a go myself at some point with the 14" once the moon is out of the way, but will need to adjust the OAG for it - oh, for a parfocal V and L filter set... Even for me, it'll still need 5min exposures to get anywhere near I should think...

Cheers - The BRATS team (Brazilian Transient Search) did the hard work in discovery - it just happened to be clear at the right time for me 😉

Catchy name 😉 Newly discovered, previously unknown dwarf nova (from spectrum by Hiroyuki Maehara (National Astronomical Observatory of Japan) - Atel #13424) - and possibly a WZ Sge type according to discussion on the vsnet-alert mailing list. I got 2 hours worth of data less than 24h after discovery, but was clouded out unfortunately at this point - another couple of hours would have been perfect! It's currently dimmed to mag 15 - I caught it between about 13.95 and 14.05 on evening of 28th Jan (19:36UT). Data (others is clearer...see the AAVSO lightcurves: https://www.aavso.org/LCGv2/) shows double peaked superhumps, amplitude ~0.04mag, period ~0.06d. All with my ST2000XM, home-made 350m Newt, from W Oxon. Exposures were 3 min through a Astrodon V filter.

Through my 14" newt, and using 2min exposures at the start - given the short period, I always find it a tough balance between getting sufficient signal to noise Vs enough cadence to resolve features in the light curve. It looked OK at the start but the SNR rapidly went downhill - I switched to 3 min at the end but the mist had already won by then!

It'd have to be biblical on the Friday to give me chance! Lost count of the Saturdays wasted waiting for umpires to call the thing off (usually after 2-3hrs of being sat around!)

This is ASASSN-20ap - discovered on 17th Jan 2020, it's a new UGSU type dwarf nova in Lynx. Currently at mag 15.05 in V band, this is a time resolved run from the 20th Jan. Conditions started OK, then deteriorated all the time with ever worsening transparency (now quite misty!). I also very quickly imaged the short period HADS star V451 Dra - easier at Vmag 12.45 - 13.05 !!

Hadn't even thought about either to be honest - barely thought beyond Feb at the moment! I'd like to be able to make it along to one - the VSS one sounds interesting, but it's in the cricket season and that's Saturdays tied up for me as I play in the league.... 😕

V799 Aug has a really interesting light curve (I've not seen anything quite as similar either) - graph looks great. Sorry to hear about your back troubles - hopefully you're back on the road to good health now! And also proven the benefit of good documentation! 😂

Cheers. Yes nice to get it all running - just about scraped through with the camera too - needed a desiccant bake as it started to frost up at one corner (but not enough to lose the data!)

First time doing any astronomy since November - weather, life, equipment all in the way. But a reasonably productive night. HADS stars NP Lyn and V1425 Tau both observed for the ongoing HADS study (graphs below - all through a Astrodon V filter). Also did a quick shot of U Gem before I then got clouded out after one single 180s image (!) and measured it at V= 13.869 +/- 0.008. Cheers, Graeme NP Lyn: V1425 Tau:

UGC 394 Very nice here! It's only 0.22 arcmin along the major axis... There is some great detail here (edge correction on what is a very fast newt with a huge sensor aside!) I would agree with @vlaiv about the filler exposures for the star cores and galaxy core - the core of M31 is saturated (not a surprise!). Using short exposures and then an HDR combine into a 64bit depth image should sort that, though of course, it doubles the filesize again in doing so... Great shot nevertheless!

I have a double truss mounted on an Equatorial mount (14" f4.53) - I didn't design it to be a serrurier either, but it's fairly well over engineered! I had trouble with the original Orion aluminium tube - it was too thin and flexed at the focuser with the weight of the camera/focuser, and the tube rings were too weak too. Here's the build thread:

Also known as h and χ Persei, the Double Cluster (comprising NGC 869 and NGC 884) is a "line of sight" pairing in the constellation in Perseus, though actually they are only a few hundred light years apart. The clusters have a combined visual magnitude of 3.7 and 3.8 and are visible to the naked eye as a fuzzy patch between Perseus and Cassiopeia. NGC 869 (top) has a mass of 3700 solar masses and NGC 884 weighs in at 2800 solar masses; the total mass for the complex is estimated in excess of 20,000 solar masses when including an extensive halo of stars. Based on their individual stars, the clusters are relatively young, both 12.8 million years old, with the hottest stars having spectral class B0; NGC884 also has 5 prominent red supergiants including variable RS Per (closest to the centre of the lower cluster). North is to the left in this view. Skywatcher Esprit ED80 SBIG STF8300M + Baader filters MI-250 mount RGB (125m:115m:115m - all in 300s subs., with additional 25x15sec in each channel for bright star cores) Taken remotely from E-EYE in Spain: * Image capture: Graeme Coates & Paul Tribe * Processing: Graeme Coates Bonus points for spotting the small fuzz of a galaxy in the field 😉

Finally removed the spiders, cobwebs, etc from my scope at home (and my word, do the mirrors need a clean... I did have to do a quick clean in place as the Daddy Long Legs spiders had almost completely covered the secondary in web!!!!) and took some variable star data. V460 And as below from 83 x 60 sec exposures through a V filter (these to go into the ongoing HADS project I've been contributing to). I tried to also grab a cycle of DW Psc, but kinda failed when I realised I was imaging through fog... (amazed it was hanging on (just) to the guide star TBH!) EDIT: properly reduced with the sequence from the AAVSO.

I haven't dealt with gradients in PS or Gimp in a long time - one way is to make a suitable greyscale gradient across the field using the gradient fill, apply as a mask and then levels to reduce the gradient. Others might have better explanations!

"Pinned to the left" is a really poor way of saying (sorry...) that you need enough exposure to overcome the read noise in the sensor. If the exposures are too short, then the read noise will have a more significant influence. It can be shown that, if read noise is negligible, then (practically) you don't need a longer sub exposure, you just need more of them [you get nearly the same Signal To Noise from stacking equivalent total lengths of exposures vs a single long exposure, but without losing dynamic range at the top end]. Reduced = calibrated (ie with daks, flats) - ie to remove as far as possible instrumental effects. Read noise can be measured from bias frames (shortest possible exposure with lens cap on) - it's a statistical measurement of the variation of pixel values between frames. Ultimately, there's no hard and fast rule as to how much greater the background count should be, but I would say yours looks overexposed (though the raw data is needed to properly show it) - here's the histogram of the first image: The data is well over to the right, probablymuch further than it needs to be, and there is clipping shown by the spike at 255. If the peak of the image is about a third of the way from the left, then you're probably fine - you've then enough data to swamp the read noise, yet you retain dynamic range in the brighter portion of the image. It'll depend on sensor, your location, your telescope. etc. I am a little confused by you method of post-processing though. From the calibrated stack, you should just be able to use Levels, which allows you to "stretch" the data, and to set the background level appropriately. Something along the lines of this levels, but you'd use a 16bit image as source rather than a jpg, and there's some colour casts and gradients to remove, the background isn't dark enough (noisy because of starting with 8 bits, not enough sub exposures in the stack, etc, etc.)

Well, you've no problem with the fields, but the issue here is the amount of exposure - you just need much more of it. Is the D5000 modded or not? If not, you'll potentially lose a lot of sensitivity in the HA part of the spectrum which strongly affects the image of the Cocoon - this will make nebula photography quite hard for you. Even with a modded cam, only having 4 or 8 min is not enough to ensure the signal to noise ratio is high enough to drag the object out of the noise (thermal, read and sky background). If you continue to take lots of subframes (ensuring the histogram is not pinned to the left), and then reduce and stack those subframes, then you'll find the image starts to become easier to stretch and display. 240 or 300sec should be fine for subexposures - you need to ensure that the background noise swamps the read noise to get an optimal length for each individual sub exposure. I'd also run at 400-800ISO instead of 1600 to preserve Dynamic range - see: http://dslr-astrophotography.com/iso-values-nikon-cameras/ which suggests 400 or 800 as optimal. Any higher ISO, and you will get the same results by stretching in post-processing. Also, beware of not making the background too dark when processing the images - rule of thumb is RGB=21:21:21 (out of 256) as a target background - it prevents you losing the faint stuff into the blackness. Good luck!

Sorry - yes, I hadn't put it well - I meant CCD binning only works in comparison to CMOS when read limited. If you aren't read dominated then the SNR doesn't increase by factor 4 (but yes, the other noise terms add in quadrature). It is important to state which realm you're working under - if you're dominated by read noise, the R squared term in the ccd equation dominates (and leads to the 4x reduction for ccds, but 2x for CMOS). You have to cope with the corresponding loss of resolution though.

Well, not really the same. CCD binning occurs on chip pre read out so for a 2x2 bin, there's one lot of read noise but 4x the signal (ish) - effectively the read noise is 1/4 as much (ish). CMOS binning is post read out, so you've got 4x signal, but only half as much read noise (sqrt(4) - errors add in quadrature). It seems a little pointless to upsample again - all you're doing is losing resolution... It is worth noting that the binning only really helps when your error terms are dominated by read noise (eg short exposure, or exposures from very dark sites/narrowband). If thermal noise or sky background dominate, then it makes not a lot of difference at all... Aperture is the important term all round - it dictates how many photons arrive from a given source. Comparing the brightness of images is not sufficient either - you need to measure the signal to noise ratio in the images. To me, the comparison images look like the second is noisier, even if it is brighter...

It's a great image - I actually prefer it with the slight pink cast in the ref neb - it's a real thing (as much as mixing in HA with RGB is in anyway "real") so have no issues with a slight cast! Great stuff!