Mike JW

I too tried it with a 20" Dob and a 15" - forget it - total waste of time and no result. Mike

Hi Flavio, Noting that I am not really following the interesting discussions above - as stated I lack the technical knowledge. You ask if details will be comparable if sampling resolution is the same. The C11 at f6.3 (which is the f ratio I use for EEVA) and the 15" at f4.5 have similar focal length and as stated I tend to use the Ultrastar in 2x2 mode for both telescopes. The 15 gets an image so much quicker than the C11 and my gut reaction is I see more detail with the 15 on moderate brightness objects. Given a choice I would always go for the 15. Often when using the 15 I will reduce the time for each sub down to as little as 5 seconds (knowing that with all that light gathering power I will still quickly get a decent shot). I then get sharper stars and I suspect sharper details in the DSOs (I could of course be imagining this as the physics involved in cameras might be saying otherwise?). As a casual observation when it comes to choosing a scope for EEVA and DSOs, my feeling is get a bigger scope as is reasonable for one's circumstance. If I had to travel to do my observing then it would be at least an 8" scope on a suitable alt/az mount. (I use to mount a C9 on the iOptron Minitower - very portable set up and the mount was good enough for EEVA style work even when loaded up with the C9). Sometimes I use my current 7" Mak Cas for EEVA - nice results but disappointing compared to the C11 or 15. Can I ask what do you mean by terms such as 1.5 x FWHM. Have fun, PS - I no longer do the hours observing that I use to - age has caught up and over the last 10-15 years cloud levels have increased noticeably (climate change and aircraft con-trails). Mike

Hi Flavio, As Martin knows my technical knowledge is poor. I am a "point and shoot" person. However having said that here are a few thoughts from someone who has observed visually in rural GB for 20 yrs, under mag 5.0 (poor night) to mag 5.7 skies (good night), using a variety of quality scopes, anywhere between 150 to 200 hrs in a year. Nights of excellent seeing are so rare that they are truly memorable - count them on the fingers of one hand in any given year. Short periods of excellent seeing sometimes happen on what is otherwise a good - ish night. Nights when I have been able to push the magnification to close to the Rayleigh limit with a scope have been rare (whether I was using a 5" Apo, 7"MN, 8"OMC, C9 or a top of the range 15" Dob.) Splitting doubles below 1" second has been rare. Nights of good seeing are more common but not exactly guaranteed. The point I am driving towards is as you ponder the best combination then work on the basis that most nights in GB are pretty average to good. Martin uses the Lodestar with large pixels (8.2 um pixels) and if I remember rightly rarely uses binning. I use the Ultrastar with smaller pixels (6.45 um pixels) and use 2x2 binning pretty well all the time on the 15" or the C11. Sometimes I try 1x1 and find it gives tighter stars but not any obvious difference in resolution. However in 1x1 mode the time to getting a decent image is much longer and for me doing EEVA is about being as "live" as possible and preferably no post image processing. It seems to me that for DSOs then large pixels are fine. I t would be interesting to compare the Lodestar and Ultrastar on the same object/same scope..... I have a friend who uses a Watec (8um pixels) on a large Dob and compared it to the Ultrastar ( no stacking but same time for the single sub). He found the Watec went "deeper" - large pixels better for a given time? SNR - casual observation on my part - after 20 to 30 stacks the detail does not improve but the background noise does get less - I like a "clean" image. (reminds what I use to see when when using big Dobs). I also remember reading that it is best to work on the practical 2-4 arc second Airy Disk - not that I really know what that means, other than that is likely to be seeing conditions in GB. I will be very interested in your conclusions. All the best Mike

Bill, Such a plus your wider fov, the shot is only missing 6107/05 at the bottom. The individual shots I used to make up the bigger picture show more detail. Thanks for adding your shot into the mix. I could try my 7" at f5 but the fov would still be more than your set up. Mike

WBL 612 (corona borealis) is a complete contrast. It is spread over a large area and I had to do four images and then combine them. There are 10 galaxies in total NGC 6105/07/08/09/10/12/14/16 and two others. The group is about 400 million lyrs away. NGC 6107 is a big elliptical - 180,000 lyrs across. 6108/09/14/16 are spirals and about the size of the milky way. Screen shot is from Sky Tools 4. Mike

Thanks Bill. Mike

No reason for it not to be classed as EEVA. Mike

Martin - thanks for the info. Bill - the reducer adapter is http://www.scopestuff.com/ss_npea.htm. What spacer do you use because that might be a smart move on the 15. Converting the f4.5 to f2.25 is a bit sever even for the quality optics of my mirror but something around f3 or f3.5 might just work. Mike

Bill - using your scope at f2.5 is a real winner - great wide view. I have tried reaching focus on my Dob with a 0.5 reducer on the camera but even with an adapter I had no luck at getting an image. Mike

Abell 2937. I find this area very confusing. Using the link in VizieR the centre of the cluster is put where the tiny red square is located (in the middle, just above the bright star.) Using Aladin the cluster centre is shown where the cursor is and given as two objects superimposed on each other with the info at the cursor given as a galaxy cluster Abell 2666 - much easier to sort and a very interesting fov. Thanks for posting. Mike

In the early hours of 24/09/20 I took advantage of the transparent (but unsteady) sky as the cloud and rain left the area. Spoilt for choice of targets so decided to concentrate on Arps - nine in total. Each one has a different character which is why I enjoy the Arp journey. My favourite from the night is Arp 331 - a galaxy chain. Arp 228 is showing a ring structure. Arp 290 shows the 'wind blown' effect. Arp 333 - just like it but Arp thought it had thin arms. Arp 229 is a superb SA galaxy (and a radio source) with its small EO companion. Arp 219 - what a great tidal arch due to its interaction with its tiny neighbour. Arp 186 is a recent merger with the tails very much in evidence. Gradually they will disappear. Arp 126 is a pair of messed up spirals. Arp 70 is a pair of interacting galaxies - note the small galaxy at the end of the tidal tail. Mike

Indeed they are interacting. Also known as VV 338. Thanks for pointing these out. I shall visit them one day. Mike Quote from an article: NGC 672 and IC 1727 -Being only 88,000 light years apart - about the diameter of one of them - they interact extensively, even to the degree that they are encapsulated in a common envelope of shared gas and intermingling stars. This pair is theorized by Zitrin and Brosch to be situated along the same dark-matter filament in an otherwise galaxy-sparse part of the universe. The theory is that the dark matter has focused the regular matter in the region, allowing it to condense into small, irregular galaxies and then into larger spirals by way of hierarchical cluster.

Here is another PN - NGC 6058 in Hercules. Now this one gets really interesting. At first glance it has the normal ring appearance with a central star. No change in my close up but start reading up..... - https://www.astrobin.com/jcjxss/D/?nc=user It is multi polar. There were 3 bi-polar outburst roughly in the same plane. Then awhile later there was fourth outburst more or less perpendicular to the other three. This last one is slightly elliptical and is now interacting with the other three. Looking closely at my shot and comparing to the web site link above it would appear that I have imaged the last outburst. https://www.researchgate.net/publication/258841668_Multiple_outflows_in_the_planetary_nebula_NGC_6058 I wonder if I would get anymore detail if did 1x1 subs and ran it with the 15 for much longer? Mike

Hi Martin - I had run out time to hunt out the details of the 'curved thing' - spaceship heading our way!!!! So thanks for finding out about it. It shows up in all the images. Mike

Abell 46 in Lyra. This a challenge even for the Dob. I kept the subs short as conditions were unsteady and it seems to give sharper stars. The central star is an eclipsing binary and angled to earth such that it is viewed (spectroscopically) as a grazing eclipse. It is thought that the two stars lie within a common envelope and it is likely that the bigger star has expanded to encompass the orbiting companion. In reality this PN is a hollow tube. Mike

Hi all, Mirach's Ghost, 891, 507 group are all visual favourites of mine. Barbon's galaxy - new to me. Bill - those diffraction spikes do it for me!!!

Bill - good to compare our different efforts/scopes/timings needed to get a result. Mike

Hi Tony, I use to use a C9 and the C x0.63 reducer, now I use a C11 and the reducer. Back focus for the reducer is 105mm but 100mm works fine. I do clean the corrector plate (very carefully) and that reduces the dust bunnies. Your results are way better than I ever got but then I was using the Ultrastar and not a small pixel camera. Mike

Hi Callum and Martin, Below is Jones 1 - hot off the press. Captured a few minutes ago. You are right as to which is the central star and yes Jones 1 is ancient. Mike

Good one. I keep meaning to locate Mayall 11 - thanks for the inspiration to give it a go. Mike PS. using your image I located Mayall 11 last night. It was handy to have the galaxy UGC 330 as a place to sync to and then I steered the scope to the right place whilst comparing to your image.

I was heading to Abell 46 in lyra but first decided to sync on M57. Noting I was using the 15, I decided to do what I think will be my last ever camera look at M57 and here it is - rather pleased with the detail. First up - the context view. The key is short subs. View is a stack of 34 x 2 sec subs. If you know where to look the galaxy IC 1296 is starting to show up but the aim of this was to capture M57 in as much detail as possible. Recently I realised that actually I know very little about M57 so at the end of the post is a few summary details - apologies to those who have far more knowledge than myself. Delighted to get the little extension to the ring, top left, and hints of other extensions bottom right quadrant. I was not expecting the two stars to shine through the ring at the top. Great to see some of the structure appearing as well. The other week I was wondering what M57 would look like in 3D. I was totally unprepared for a 'tilted slightly elongated football' inner cylinder of hot principally ionised Helium, surrounded by a doughnut shaped ring of expanding ionised gas. The outer ring contains ionised nitrogen and oxygen (O111) which make up the characteristic red and green colours. Other atoms of note are flourine, neon, sulphur, argon and chlorine. The orientation of M57 is toward planet earth and thus we see a ring with a central cavity - we look straight down the central cavity. In my naivety I had not picked up that beyond the ring that we see in visible light is yet more gas that has now cooled and expanded to low densities. Its distance from us has been a matter of discussion and currently has settled to 2300 lyrs away and getting less as M57 is heading towards us at 21km/sec. The ring is expanding at about 20-30km/sec. https://www.spacetelescope.org/videos/heic1310e/ - well worth a look. Next post will be Abell 46 - the real aim of this Lyra jaunt. Mike

Hi Martin I love going back to past glorious sights - changing sky conditions and you never know what extra detail may appear. False Saturn's are surprisingly common.

This thread can be used to post shots and info for WBL Galaxy Clusters. Info below from an article. A catalogue of 732 optically selected, nearby poor clusters of galaxies covering the entire sky north of -3° declination is presented. The poor clusters, called WBL clusters, were identified as concentrations of three or more galaxies with photographic magnitudes brighter than 15.7, possessing a galaxy surface over density of 104/3. These criteria are consistent with those used in the identification of the original Yerkes poor clusters, and this new catalogue substantially increases the sample size of such objects. These poor clusters cover the entire range of galaxy associations up to and including Abell clusters, systematically including poor and rich galaxy systems spanning over 3 orders of magnitude in the cluster mass function. As a result, this new catalogue contains a greater diversity of richness and structures than other group catalogues, such as the Hickson and Yerkes catalogues. The information on individual galaxies includes redshifts and cross-references to other galaxy catalogues. The entries for the clusters include redshift (where available) and cross-references to other group and cluster catalogues. I am currently working on a list that will include constellation name and names of key galaxies (NGC, UGC, IC), now added (26/09/20). Not all the WBL groups can be located using the NGC, UGC, IC. WBL galaxy cluster list.xlsx https://vizier.u-strasbg.fr/viz-bin/VizieR-3 - gets you to the VizieR tables 19/09/20 WBL 611 in CRB. Includes UGC 10283 and 10285. The three members are bright galaxies in a spaced out triangle but there are other galaxies in view. Mike

19/09/20. Palomar PCG J1525+2956. Found in CRB. Poor conditions and low down so not easy to get a clean image. Four members, about 1.5 billion lyrs away, mag 16-17. Other galaxies picked up as well

To parallel the EEVA thread on Planetary Nebulae, this thread can be devoted to Reflection Nebulae. To start the ball rolling here is an observation and notes from last night (19/09/20) PARSAMYAN 21 - found in Aquila. When this 'little comet' appeared on the screen - I had yet another one of those WOW moments. I get a real buzz out of seeing things with the EEVA technique that otherwise would be elusive. This reflection nebulae set amongst so many stars is wondrous as far I am concerned. and so to the scientific detail. Parsamyan Nebulae (also spelt Parsamian) are reflection nebulae. P. 21 belongs to class V - comet like nebulae. This is where the parent star is at one end of nebulosity (which can be in a ring shape). The parent star is young and sheds material but something causes the release of gas to be directional. In the case of P.21 the suggestion is there is a disc of stella material or a torus (doughnut) of material causing the directional shape. P.21 takes the form of an elongated tube which is closed at both ends. The star lies outside this tube. Light polarization studies reveal that the dust on the reflection nebulae is small grained but at the star end and also surrounding the star the polarisation changes direction suggesting that there is indeed a torus of stella material causing the direction flow - hence the comet. Mike