Martin Meredith

Hi Peter Nice report, and good to hear about the visual comparison. Were you doing much in the way of histogram adjustments? You ought to be able to see plenty of stars in a 1s exposure but only if the black point is appropriately set, and the image stretched. Alternatively, it may be that your overall focal ratio is quite slow for EEVA. The selection of objects you've chosen is rather challenging for EEVA techniques. Planets (apart from Uranus outwards) require a different approach to DSOs, and M45 and M31 need a large FOV to make an impression, so it perhaps isn't surprising that the visual views equal or better the camera views. If you were to look at planetary nebulae, globular clusters or (especially) galaxies/galaxy groups, you'd immediately notice that the EEVA view goes many many magnitudes deeper. cheers Martin

Thanks Rob. It looks like it is removing far too many hot pixels so the threshold needs to be raised I would say. But in any case, if you could PM me a few FITs (5 if poss so I can see the hotpix) I will check it at my end.

51 And (mag 3.6) has no Bayer designation that I'm aware of... and mag 4.1 HR4522 in Centaurus has neither Bayer nor Flamsteed (found by trawling through the XHIP bright star database, sorted by increasing magnitude) The same source suggests gamma Vel (or at least gamma^2 Vel) is known as Suhail al Muhlif, which would make del Vel (mag 1.9) the brightest without a proper name. It might be that Suhail al Muhlif is not an IAU name (I haven't checked).

Odd. I've not had a failure in hot pixel mapping so far and the feature has been in since the start, but then perhaps its not been tried with such a short focal length (not that it ought to make much difference). Perhaps worth checking the logs (in joculardata/logs) to see if there is anything odd going on that is preventing the hot pixel mapping from getting deployed. Feel free to send me the log 🙂

Could you check you have hot pixel removal set to on? (Config icon then badpixelmap). There is also a parameter that controls the outlier rejection threshold. Try lowering it slightly if the hot pixels are not removed. To rerun the stack after any changes, just hit the recompute stack icon (at around 11 o'clock on the eyepiece).

Lovely shots Rob. Amazing what can be done with a fast 66mm scope. SLL is one of the few capture programs that don't write exposure time into the header. I used to estimate it from sub arrival time intervals but that wasn't universally reliable. There is a way to read exposure info from the user but this is being simplified in the upcoming version so I won't confuse things by going into the details here. I'm also hoping to provide the option to edit the exposure info for previous captures soon. Hot pixel removal ought to be on by default, so in general there is no need to use median just to remove them. For the odd frame with satellite trails I often just deselect the offending sub, but for slow-moving trails I tend to use the 90/80/70% percentile options if i have enough frames. SNR is slightly worse with median than with these other options, but it is pretty marginal.

I started off my EEVA journey with a good quality 2nd hand achromat (StellaVue Nighthawk, 80mm f/6) and, to be frank, I found the CA really annoying very quickly. It was fine for the first few months as the EAA bug bit (everything looked good!), but once I started to look deeper the bloated stars that were present every time in every image were a real turn-off. I went for a Newt and never looked back. Honestly, unless you already have an achro to try out, I wouldn't recommend buying one specifically for EEVA.

Hi Jonathan Welcome to SGL! Some people do a great job of EAA with Dobs on eq platforms. Check out Tiago Ferreira's YouTube channel for instance. He's active on CN (maybe here too) so would be able to answer questions about tracking. MikeJW uses a driven GOTO dob and produces excellent results with an Ultrastar camera. Finding objects could be tricky with a small FOV. Being able to platesolve frequently while finding would no doubt help. Its a direction I'm planning to go down myself soon, as it happens, but using a push-to 10" dob on an Asperion platform. My main use case will be visual as I now have access to darker skies. My rationalise is that a platform brings its own benefits for visual too e.g. easier to up the magnification or study details, and if it also works well for EAA that will be a bonus. Do let us know how you get on. Martin

If you can control your camera directly from Sharpcap then I'd suggest continuing to use that rather than Jocular, because Jocular has only rudimentary support for OSC cameras and is likely to stay that way for a while. Jocular is mainly geared towards mono or colour through mono + filters.

Half the fun is finding these things. Sometimes the colour is a dead giveaway. I've observed NGC 6567 and totally agree about the rich star field, typical of the area. In my shot the planetary is distinctly blue, as you're getting too. There's a great triple at the right edge of the field (HJ 594) and I hadn't noticed the lovely arc of stars just to its lower right on my shot. I'll have to add NGC 6537 to my list. I have a few more degrees of dec to play with here at 42 deg... Martin

Cheers Rob. I knew Callum @callump was writing an article but I no longer get Astronomy Now -- I will try to pick up a copy when I'm in the UK soon 🙂

Hi Ian Welcome to SGL! I'm not sure how much help I can be as my kit is a bit different from yours (I use an 8" f/4 Newt) but I'll try and hopefully others will also chime in. Alt-az is absolutely no problem for EAA. Since 2014 I've only ever used alt-az. With modern cameras you can stack short exposures (5-15 seconds) and not suffer from field rotation within each exposure, and the software automatically handles field rotation between subs. Fast is typically best as you noted, so using your 9.25 scope with a reducer is going to help. At the same time you may be able to use it without the reducer for small DSOs, but what really matters here is the field of view, since you need to be able to find the objects in the first place, and get sufficient stars to stack. In principle all you need is a laptop and a camera attached by a USB cable. If you plan in the future to operate remotely (e.g. you in the warm, the scope outside), then using your RPi4 to control the mount and wifi the images across is a possibility, but I wouldn't start with that level of complexity. That really leaves the question of the best camera. I think its fair to say that most people in EAA use astronomical cameras rather than stock DLSRs, in part because the software support for EEA is more seamless for astro cameras. So if you're lacking something from what you already own it is a suitable camera. There are a lot of choices. If you haven't already done so, can I suggest that you visit http://astronomy.tools/calculators/ccd_suitability to see what camera will provide decent sampling for your scope (with/without reducer), and http://astronomy.tools/calculators/field_of_view/ to check out the field of view you can obtain. Note that most DSOs fit comfortably into a field of view of around 0.5 degree square, but for larger objects like bright nebulae you'd need a bigger FOV. Large sensors come with their own issues (cost and vignetting). That said, it is possible to do EAA with the cameras you already have (just that I don't have any experience with them). As for software, most people use Sharpcap (Windows only) or ASIlive (ZWO-ASI cameras only). With your potential setup you'll be able to see 1000s of interesting DSOs from a Bortle 5 zone. Anyway, that's just a start, so do get back with any further questions Martin

I've been meaning to get round to this one day, so thanks for producing this video. Meanwhile, longer USB cables (one for the camera, one for the EFW) have been serving me well. I've even had them trailing out of the windows of my campervan. The only problem is they're not quite long enough to have the scope sufficiently far away to see over the top of the van...

Excellent first light review! There is something very appealing about combining the ease of use of a dob with the ability to find targets quickly, and all without spending time on aligning a goto system (the most tedious part of the process for me, and generally not all that accurate...). I see that you waited for close to maximum darkness, but do you have any feeling for whether the platesolving works during late twilight? Martin

It looks like the primary mirror cell/adjustment is completely different from the one in the Alan Dyer review (near the base of the page). i wonder if this is a 10" vs 8" difference or whether they've modified the design already.

Thanks for this review and here's hoping you have a clear night soon. I'd be interested to know how well the focuser and tensioner handles heavy eyepieces, esp. if a coma corrector is also used. My last reflector was f4.5 and really needed a corrector but perhaps at f4.7 it won't be needed.

I'm sure we must have had Arp 286 in Virgo before but its a new one for me (at least in the recent past where I've kept records...) This is in the 'double galaxies with infall and attraction' category, and consists of NGC 5566, 5560 and 5569, in order of brightness. NGC 5566 is SBab(bar, ring, mult) according to LEDA and SB(r)ab according to the Kanipe & Webb Arp book. NGC 5560 is SB(bar, mult) for LEDA and SB(s)b pec for Kanipe & Webb NGC 5569 is SABc(bar, mult) or SAB(rs) cd: -- take your pick. Either way, this is a very interesting selection of barred spirals that fit easily along the narrow axis of the tiny ASI 290 sensor. I would have left this for longer but seeing was worse than 4.5" and detail didn't seem to be improving, but it is one to revisit as there is a lot of structure and extensive faint detail to extract. This image is quite noisy as I've tried to show the extent of the spiral arms in NGC 5566.

Abell 2151 is a marvellous group and is one of the few that has me hankering after a larger sensor. One could easily spend an hour or two in the this area alone. You're right that Arp 272 appears to be wrongly labelled (also the case on my charts). Having checked the Kanipe & Webb Arp book it does mention a naming irregularity and that Arp's original atlas indicates NGC 6054, which is where Jocular places its circle, and indeed Simbad http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ngc+6054&submit=SIMBAD+search agrees with this (erroneous?) designation. All v interesting for the astro-historian no doubt! We're just fortunate to have so much to see in one shot. Here's mine from earlier this month:

Try this version. A zero in the SAO column indicates no SAO star found within 0.01 of a degree in both RA and Dec. There are SAO numbers for about half of the 3000 or so in my list; ideally these will correspond to the main DS designations. doubles.csv

Here's STFA 33 in Hercules, discovered in 1835. The pair are not particularly close (305") but their similar magnitude and contrasting colour make up for that. The blue-ish star is mag 5.9, type A1, while the yellow-orange companion is mag 6.1, type K1. The system on WDS has 3 further components: the peachy mag 8.5 star at the top is the C component, known as ARN 15, the faint mag 10.4 star between A and B is D, and the mag 11.0 star below the D component is E (I think I've got that all right...). The chosen stretch matters a lot when trying to pull out natural looking star colours. I tend to use small-exponent gamma for luminance since it matches the colour stretch (which is also gamma). But applying the stretch function I often use for faint galaxies shows there's much more going on in this field (including a lovely linear triple asterism):

Thanks for posting this. Coincidentally, I observed NGC 3521 in EEVA mode on May 7th (just 5m20s worth) and thought I detected a dome of gas orthogonal to the plane of the galaxy, and your magnificent image confirms that there is definitely something there. Martin

This field in Serpens containing STF 1987, discovered back in 1783, is a case of 2-for-1 as it also contains the fainter pair TOB 255 (disc. 1842). Luckily for the observer a range of spectral types are on display here. The brightest star is a mag 7.3 A0 type, B-V 0.26 with a blueish tinge, and its close pale yellow companion at 10" sep is type B6, B-V 0.48. I don't have spectral info for the TOB 255 pair but I'd guess they're cooler K or M types. Their most recent separation estimate is 15", so not that different from STF 1987 but seemingly more so due to their being dimmer.

S 665 in Libra is another near equal pair. HD 133353 on the right is a mag 7.9 type K2 star with a B-V colour index of 1.25, while its companion is mag 8.8 of slighty earlier K0 type and commensurately lower B-V of 1.04. The slight difference in hue is just about visible here. The position angle (91) and separation (25.1") has barely changed since the discovery of the system back in 1828 -- optical? An interesting optical/physical debate: https://www.cloudynights.com/topic/495354-most-doubles-in-wds-are-optical/

Hi Mike The L and T classes are the cooler extensions to the OBAFGKM sequence added around the turn of the millenium. At that time there was also a still cooler class (provisonally named 'Y') with no members known, but perhaps by now some have been found. Its at this point where the stars and larger planets start to overlap in temperature and chemical element abundance. T for instance contains a strong methane absorption. I use the 2nd (2011) edition of Kaler's Stars and their spectra, an excellent and nicely technical guide to the stellar sequence. There is almost no emission at visual wavelengths so we're relying in near-IR capabilities to pick up anything at all. I'm pretty sure I picked up an L class (not part of a double) some years back but I ought to revisit. As I recall it was fainter than 19th mag in the V or B band. I'll continue to look at using shorter subs. The trick might be to use short subs in L only. I've added a FWHM calculation to Jocular which so far suggests my seeing (or focus, or tracking... its all confounded) is pretty poor much of the time (worse then 4"). You'll be able to use it with previous captures to see what your seeing is like at some point. Martin

Here's one I'm not sure about. This is a relatively recent discovery from 1998, DEA 84. (BTW, if you're searching for these in the WDS or elsewhere, the discovery codes are all 7 characters and use multiple spaces to make up the count, so there are 2 spaces between DEA and 84) The primary is an M0 class mag 8.1 star, hence pretty red, and the companion is a mag 14.3 class L2.5 star. The question is: have I captured it? The position angle is 211 degrees and the separation 29.2". There is a faint star at around 210 degrees (where I've placed the DEA 84 label) but it looks to be a little too far out? [Edit] definitely not caught it! Looking on Aladin there is a label a little further in but one has to look on the PanStarrs/DR1 tab to see a dark red star in that place. No V mag is listed; the 14.3 corresponds to a K-band magnitude....