rl

It might be worth managing the op's expectations here...Regardless of the scope choice Mars will still be miniscule until the next opposition. For a considerable outlay, Jupiter and Saturn will be slightly less small and showing a bit more detail. Since both are fairly low at the moment, the seeing may well be the limiting factor rather than the scope. Your EQ5 mount would not normally be considered stable enough for general long-exposure photography but you might well have some success doing lucky imaging of the bright planets where slow movement of fast exposures around the frame is less important, and removed on stacking. Planetary cameras with a high frame rate are not expensive by the standards of this hobby. Maybe it's worth going to a local society and having a look through someone else's scope, certainly before committing to a Classical Cassegrain. The Skywatcher 200 PDS is a good choice for a medium-large general purpose Newtonian but it's probably not the easiest way to start photography. Most people start with wide field deep-sky with a small fast refractor. If you are thinking of deep-sky photography, the usual advice is to concentrate on the mount and guiding rather than the scope!

Reflectors don't show chromatic aberration, but eyepieces do (especially on venus), and the atmosphere is one big prism, particularly near the horizon. I suspect the atmosphere was the major culprit on this occasion. You can even buy dispersion correctors to get around this problem.

Result! Superb shot.

It's the wavefront. They make the point about the 2:1 ratio on their website somewhere. They also miss out the secondary shadow zone which is fair enough. I don't think the test includes the secondary but I might be wrong on that one.

This looks superficially like an OO zygo test certificate. All of theirs I have seen have a few extra details though...telling the data and time of the test, and the size and focal length of the mirror, and its serial number, and the wavelength at which the test was done, and the operative (usually R Rogers) The numbers on yours are typical of an OO 1/10 wave mirror. On wavelength, OO use a 632nm HeNe laser so 1/10 wave is more like 1/8 wave at 550nm where the eye is most sensitive. Attached is the one for my VX14 for comparison. Without full details tying the report to a particular mirror, there is no traceability. I would be a bit suspicious...

Thanks @ JeremyS. Don't know why. One of the better frames:

Bit of a change of plan last night. Life called off the dark sky / good seeing excursion with the 14" so I set up the 6" refractor in the garden to have a peek at Jupiter and Saturn. Dubhe is unfortunately behind the house. Planets a were not much good due to seeing, so I tool a leaf out of John's book and tried Lambda Cygni instead. It would be good practise since the separation is about the same (0.9 arcsec). The brightness difference between the two components is not so great as Dubhe but it would be a good training target to hone skills and manage expectations. Oh the joy of using a decent driven equatorial mount on close doubles! Whereas in the Dob the other night it was a right pain nudging the scope with one hand while trying to damp off the vibrations with the other...the star just sits where you want it with the eyepiece at a convenient height! Much easier to concentrate! Lambda Cygni was resolved as double quite easily if a bit messily using a 4.7mm Ethos (*320). The B component was a very striking blue compared to the white primary. Seeing good for round here but not spectacular. Inspired, I put the planetary camera on just to see if I could get an image of the split. To make the scope's resolution the limiting factor rather than the camera I put a *2 Barlow in the system but this resulted in a more than expected increase in focal length since the spacing is not as intended. The focuser had to be racked right out and the whole camera setup was clinging on by its fingernails...I'm not sure the optical axes are properly coaxial which explains some slightly oval star shapes not seen visually. The blue colour of the secondary was even more apparent on the monitor at night; it's not so obvious viewed in daylight. Video clip attached; this is 105 images taken with 1 second exposures on a 6" f/10 triplet, Barlow stretched to officially f/20 but probably f/30 or f/40 in reality. No filters. I had rather dismissed the refractor for Dubhe as just a bit light on resolving power. But based on this it's worth a try. It's certainly going to be harder just down to the magnitude difference. A blue filter might help. 00_20_10.avi

I noticed this post in early May and have been trying to split Dubhe on a few good nights since. I've been using my 14" Dob but seeing has usually been awful with the star just a splodge at *230. But last night was tantalisingly close...after an hour of cooling, occasional diffraction rings were visible over an hour around midnight. There were hints of doubleness (duplicity?) with the secondary looking suspiciously like the same colour as the primary. However I can't claim it yet. With the forecast looking good this week I might take the scope out away from the buildings on the housing estate where I live and give it its best shot.. I've got a 6" refractor but I think the close separation, while being on the Dawes Limit will be too close given the difference in magnitude.

I had exactly the same issue: You can get a red dot finder that clips on to the hotshoe on the camera. I only found this out in a reply to my own review..worth its weight in gold.

This is word for word my own experience...

It's difficult to add much to Nephilim's excellent answer but I would stress it's not just a cash investment here. It takes a lot of time and frustration learning all the software to process the images and to guide the mount; It's worthwhile getting kit that will produce good quality subs in the first place just to keep you motivated. Th Star Adventurer/ DSLR route is a good place to start and will always be useful for holidays/ portable operation. Above all it's simple. If you get the bug, you will outgrow it fairly quickly and the next step up is where the spending really starts...

A few notes attached... nova_herculis_june2021.docx

Looks good. Here are spectra by Hugh Allen and David Boyd at around the same time from the BAA spectroscopy database https://britastro.org/specdb/data_graph.php?obs_id=9977%2C9978&multi=yes&mix_flux=yes There are two clear broad lines with P Cygni profiles. H alpha with emission at 6563A and another line with emission at ~6350A (Si II ?) both with absorption at about 80A /3700km/s to the blue (P Cygni shape profiles) The features to the red of H alpha are mainly telluric absorption bands from O2 and H2O in our atmosphere (Note the dramatic change just 2 days later in my spectrum up the thread) Robin, Jeremy, I'm going to do a proper writeup on this with all the details in. RL

After a lot of faffing about learning how to use Vspec I got this spectrum from my data taken around midnight on the 12th - 13th June when it was at its short-lived brightest (X-axis in angstroms calibrated with a neon lamp): No idea how valid a result this is..did anyone else get a spectrum? Seems to ba a symmetrical dip and peak either sie of the Hydrogen Balmer line at 6563, plus other wide absorption lines. Six 10-minute exposures all gave the same result.

Both are brilliant shots, better than I ever achieve regardless of the scope. I would agree the Mewlon has the edge. But it should do with a 50% advantage on resolving power, assuming the pixel size is correctly matched.. I wonder what the result would be if the exposures were balanced...the refractor shots look a little darker to me, possibly down to the slightly slower f ratio. For me it's something of a moral victory for the SW.

Heard about this nova on this thread early this evening after a long, long day. Was in two minds whether to get the kit out or not...in the end I made the effort. I managed to get some spectra subs taken on my 8" Newt with an Elliott Instruments CCDSPEC. I've had the thing for years..this will be the first time it's been used in anger. One raw sub shown below; hope I got the right star on the slit! I got about 60 min of data in total; Hopefully there might be enough to drag a few lines out of the noise and work out the expansion velocity once I've got the spectrometer calibrated in the morning.

If you're prepared to go secondhand the 24mm Maxvision 68 degree can be a good option. I bought mine secondhand on ABS 7-8 years ago for about £50 and it has never been a source of disappointment, even in fast scopes. It's comfortable to look through with an adjustable eye guard. Aberrations are not zero but very well controlled. I'm always impressed by just how bad it isn't when compared to much more expensive tackle. It has survived many an eyepiece cull over the years. Sadly no longer available new, Maxvision were rebadged Meades as a result of some contract mess-up, but I think the same optical design has been cloned several times over and is probably still out there as a badge-engineered new product . Others will be better clued up on the clones than myself. Imitation is the most sincere form of flattery..

2" Barlows definately do have their place. My main objection to Barlows in general is that you're never quite certain what the scale factor really is because it depends on the distance between the Barlow lens to the eyepiece's focal plane, which is all down to the eyepiece metalwork design. A *2 barlow can be anywhere *1.5 to *2.5.... They are very useful in faster scopes for planetary/ lunar photography for matching the pixel size to the focal ratio. They make off-axis eyepiece aberrations less obvious in my experience. YMMV. They can be very useful in "extracting" the focal plane further out if your scope does not have enough in-travel on the focuser for some accessories. The focal plane moves more than the real linear mechanical movement on the focuser as you turn the knob. The increased focal length can be either a problem or a blessing depending on context; but at least you have options. I have a spectroscope which is quoted as being suitable for f/5 to f/30 scopes; adding a *2 2" Barlow optimizes the optical path for a f/4 Newtonian while allowing a tight and strong mechanical connection.

I followed this star during the 1980s with a 5" achromatic refractor until it got too close to split..somewhere roundabout 1992 I recall. I remember it appearing as a figure-of-eight with a waist at that time at about 0.9 arcseconds. It's one of only a handful of doubles where I've seen a change in my observing career. If someone can split it now with a 20" Newt that would be testament to both the scope and the observing site!

If by "transparent" you mean "least light lost" then the Plossls would have to be in with a shout. Less glass is usually better in this respect. This assumes the coatings are the same as the more expensive offerings which may or may not be true. I'm guessing the shorter focal lengths in any given range would have thinner lenses which may convey a slight advantage. Having minimum glass in the eyepiece used to be big thing for many observers just to cut down the light lost, but modern glasses and coatings have made possible transmissions in complicated eyepieces which are not that far behind the minimum glass offerings, and future improvements will only make the gap smaller. But it's mathematically true that, for given glass types and coatings, the simpler design should transmit more light. Whether it's worth bothering about is a different matter. More basic considerations like magnification aberrations, and FOV would normally determine your eyepiece choice. It's probably more important comparing the same focal length from different manufacturers. Zeiss orthoscopics seem to have the best reputation in this regard. A more relevant point might be what happens to the lost light. If you lose 5% of the light absorbed in the glass or scattered out of the field of view , that's not too bad. No-one will notice a 5% loss. if it comes back into the field of view as a ghost then it can be really very annoying.

The mount needs a clean source of DC from 12 to 14 volts, called a power supply. You need to choose its current rating; add up all the 12 loads like the mount (use the slew current..it's a lot higher than the tracking current), dew heaters, cameras, whatever else. 10-12 amps is a typical total number if you don't have access to all the individual numbers. If in doubt, go higher. Then you're in a position to buy the power supply from someone like Nevada. The power supply needs 12v connectors to suit. The car cigarette lighter plugs have become standard..personally I hate them because they can come loose easily I use a Farnell 0 to 30v supply but I'm not sure I'd recommend it just in case a spot of finger trouble in the dark turns the voltage up. A specialist 12v supply or 13.8v supply is better. A modified 12v 10 amp laptop power supply is another option; they are small, don't generate much heat and are cheaply available on ebay. But you need to be certain what you're doing changing the 12v connector so possibly not the best bet if you have no electrical experience. Battery chargers are not a good idea since the output 12v is not always clean. You can get mains to USB chargers that should be ok for the quark. If you add up all the bills buying proper new stuff you might find the costs are not that far short of a new battery...

Yes, it's fine but common sense applies.. I power all my gear off the mains when doing photography at home. Everything is powered through one extension lead which has a safety Residual Current Detector (RCD) plug. This will trip automatically if the current in the live is not the same as the current in the neutral because current is leaking out to ground (potentially through you!). You want all the exposed metalwork either grounded or double insulated. Commercial stuff that comes with 2-pin mains connections should already be double insulated. I can't see how even a big setup will take more than a couple of amps at 240v (500 watts) unless you're using a hairdryer for dew prevention.

There may be a "time of life" element to this discussion. It's one of the great ironies of the hobby that by the time a lot of us can afford the best, our eyes are on the wane and less able to use the optical quality. I've seen huge magnifications quoted in this thread..for me even *50 per inch shows up a lot of floaters..an exit pupil of 1mm is about the smallest I can go without having to continually move my eye to dodge the dreaded diffraction patterns produced the detritus in my eyeball. A magnification of *200 produced on a 14" is much more satisfying for me personally than on a 4" refractor. however good the quality!