Captain Scarlet

Perhaps one could take a photo of a uniformly flat target and measure the SNR at a series of locations across the whole field. One could then infer illumination from the SNR? I might take that photo and do the measurements...

On 12/11/2020 at 12:27, vlaiv said:

... I reckon that skymax 180 illuminates about 30-35mm due to having 30mm rear baffle and only 25mm exit hole at the back of the scope. ....

I have recently thoroughly measured my Skymax 180, and it turns out that with the supplied 2" back and diagonal its focal length is close to 2900mm rather than 2700mm. I suspect the 2700mm is left over from the days when it was supplied with a short vb and 1.25" diagonal.

I determined its focal length by taking photos of stars, and in the process also discovered that its image circle is about 40mm. See the pic here, taken with a full-frame Canon EOS 6D:

Funnily enough It was an unforecast clear night last night just before I went to bed, so I took my 12x50s out. One of the objects I looked around for was M33, and was able to notice it quite easily. It sits nestled in a little triangle of stars. But there's no structure on view, you really need AP for that, and it's such a low-contrast object that only the big FoV that binoculars give you will show enough contrast to notice it. A telescope spreads the contrast over such a large area that it becomes impossible to notice.

Cheers, Magnus

On 10/10/2020 at 15:38, johninderby said:

The optics are made by JOC and just as good as the Skywatcher. Nothing to choose between them opticaly. The build quality of the Bresser is better however and they are beter equipped. 

My 10” dob will handle about 400x on the moon.

You mean the famous @JOC: STEM ambassador, keeper of ducks and chickens and maker of 6" parabolic mirrors?

1 hour ago, vlaiv said:

Hi and welcome to SGL,

I second the Skywatcher SkyMax 127.

This particular version is interesting:

https://www.firstlightoptics.com/sky-watcher-az-gti-wifi/sky-watcher-skymax-127-az-gti.html

as it comes with mount head to track objects which you control via your smartphone. Only problem being the stock at the moment - most of items are out of stock due current circumstances so you'll have to spend some time finding retailer that has them in stock or to backorder and wait a bit.

this was my own very first scope, and if available at the time I would have gone for exactly this mounting system too.

On 07/11/2020 at 18:02, faulksy said:

New secondary for my 20" dob.

How thick is that 

looks like about 29mm to me...

M

1 hour ago, chiltonstar said:

Thanks. What is the mirror size and spec?

The night before I took the image above, I was looking visually - the view was near-NASA like, with excellent seeing, but unfortunately when I got the EQ mount out, I crashed the scope into the RA motor and had to remount the motor the next day.

Chris

I have a Skywatcher blue-tube 12" newt, and I'd ordered myself a new 1/10 wave 300mm f/5.3 primary from Orion Optics to upgrade it. When it finally arrived the previous weekend (scratched actually, but that's a different story) I simply swapped the mirrors over, slightly different f-numbers notwithstanding, to take some photos to establish its exact focal length prior to me ordering a new longer carbon tube for it. Obviously I had to look at Mars too and I'm glad I did! Extraordinary view, NASA-like describes it well, I thought I was looking at a Mars atlas at moments, it was freezing into amazing clarity.

I hope your motor or mount not damaged?

M

Great image. Incidentally your image corresponds almost exactly with the eyepiece view I had using my new mirror early last week. Far and away the best view I've had of Mars.

M

... if you could knock up a Televue set I'd be your first customer. Actually second after @John. The supplied TV ones I agree are not very good.

M

I have 2 Skymaxs, a 150 and a 180. As all above have suggested, you can obviously focus using the "native knob", which actually works fine, or you can add a Crayford focuser to the back. I do have Crayfords for my Skymaxs, but increasingly I simply use the knob. The problem with the knob is that it rotates a nut around a threaded bar the other end of which is attached to a bulkhead-and-sledge to which is bonded the primary mirror, which slides up and down the central baffle tube. To allow this movement, the outer baffle tube (to which the primary mirror is bonded) sits around the inner tube, and there is necessarily clearance and lubrication. Turning the focus-knob causes the outer tube to very slightly tilt with respect to the inner, causing the mirror to very slightly change orientation. At high magnification, this results in "image shift" as you focus.

The Crayford avoids this problem, but it has 2 drawbacks (no pun intended). It makes the scope very back-heavy, and it significantly increases the focal length, of the order of 200mm in my Skymax 180, probably slightly less in the 150.

Another upgrade, which I have done, is to buy the Feathertouch FTM-CPC8 upgrade to the native knob. It's very good, but expensive.

Finally another tip: I was finding my Skymax focus knob to be very "stictiony". I solved this problem by realising that the rubber knob is actually just pushed on to a big steel cylinder, and the rubber was in direct contact with the back end of the scope, and would stick to it. Just pull the knob out 0.5mm or so to avoid the rubber contact and you'll find it to be very smooth.

I hope helpful, Cheers, Magnus

My 12" blue-tube SW has a steel tube and is slightly over 20kg. Finders, rings, eyepieces etc bring it to around 26kg on the mount! I'm in the process of ordering a carbon tube for it which will save me around 4kg. Aluminium is only slightly heavier than carbon when you add in the foam or honeycombs needed to create the tube, so those OO weights make sense.

12" doesn't sound that much bigger than a 10", but the 3D size, and therefore the weight, scales up as the cube of linear dimensions (perhaps slightly less as the mirror doesn't always change thickness). I have both 12" and 8" SW newts from the same stable. 12x12x12/(8x8x8) = 3.375, and my 12" is indeed around 3 times heavier than my 8". The scale-up from 10 to 12 is 1.728 so you're looking at nearly twice the volume and weight for a "mere" 2 inches difference in spec. The 12" is truly huge.

M

On 20/10/2020 at 17:00, ScouseSpaceCadet said:

If you're in need of immediate dust protection; a black bin bag secured with an elastic band or bungee...

I was in immediate and urgent need of rain protection last night. It was forecast perfectly clear, as it indeed turned out, but what wasn't forecast was the violent little squall that came over after I'd spent 20 minutes hoiking out and setting up my big mount and 12". Black bin bag and bungee was exactly what saved the night!

I’m not sure whether this is an Observing Report or more about the kit. Oh well. I plan to write up my whole “mirror experience” more fully in due course, so below is a taster.

A few days ago I took delivery of a brand new 1/10 wave Orion Optics 300mm mirror, after a 5 month wait. I plan to specify a new carbon tube for it, as this mirror has a slightly longer focal-length than the one it’s ostensibly replacing, my blue-tube SW 300p. The new mirror requires the secondary to be further up the tube than the current one will allow.

But in order to properly specify the new tube dimensions, I needed to be certain of its focal length. Orion said “they generally come out 1590mm +/- 10mm” but I wanted to be sure. So I planned to just plonk the new mirror into the cell and use it “as is” for now, and photograph the environs of Vega to establish the FL, albeit operating at only about 270mm effective aperture instead of 300mm.

I did the mirror-swap over the weekend and set up last night, Tuesday (pre-US Election), with lovely clear skies. The Milky Way was fully on view ahead of Moonrise. Having spent half an hour re-collimating everything, I was ready to go. Because of the extra 90mm focal length, and still the same tube, I needed all the adapters I possessed to achieve focus, resulting in a ridiculously long stack. Knowing how flexible these tubes can be, I suspect the arrangement wasn’t the best for collimation!

First Light

Of course with a new toy I had to do SOME observing, so I immediately headed off to Mars. I’ve looked at Mars quite a lot this season, as we all have, and had some very decent views. But none like this. I don’t know the names of any features except the Polar Cap, but at times it seemed as if I was looking at an atlas of Mars in a book: from time to time everything would freeze into an incredible clarity of detail. The dark features across its middle looked like a “walking man” with arms outstretched, torso and legs. Quite extraordinary, and looking back over my house as well!

How much was due to the new mirror I don’t know, but from looking at Polaris it was plain the seeing wasn’t the best. I moved over to the Moon, and that too was as good as I can remember, I even said “wow” again.

I slewed to Lyra in prep for my calibration-photograph and of course couldn’t resist the Double-Double. They were easily split but Lyra was starting to sink into lower-down murk at the time and it wasn’t the best view I’ve had of it. I took my photographs and estimated a focal length of 1587 mm, although I couldn't quite (though very nearly), achieve focus with my DSLR, given the combination of adapters I had: too far out or too far in! I'll do it again. Funnily enough, the calibration picture I did take shows the coma inherent in a Newtonian quite well. The doughnuts start to become skewed really not very far from the centre. Vega's doughnut itself is round and central, showing there was no coma in the middle.

Cheers, Magnus

I have a SynScan WiFi dongle which I believe you can stick into any SW Alt-Az mount: I use it on my AZ-EQ6. I then use the SynScan Pro App to control it, from my iPhone. It all works much better than just the handset alone. I can even use SkySafari at the same time to control the mount if I wish.

Cheers, Magnus

The big dustbin (12" skywatcher solid-tube) can only live in the garage, next to the hot water tank. The others continuously move around the house until they get discovered: "you can't leave that there". So I hide them somewhere else.

Obviously it's nice to see Orion again at this time of year at approaching reasonable hours. I've lately taken to searching out and enjoying two of the little ones, Delphinus and Lacerta. I like the way the North end of Lacerta is like a miniature version of Cassiopeia.

Oh dear 4 pour moi. hilarious

1 hour ago, astromog said:

I don't think you can buy them on their own, so not sure what it's called, but the standard one that came with the scope:

https://www.firstlightoptics.com/az-goto/skywatcher-skymax-127-synscan-az-goto.html

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p4622_Skywatcher-GoTo-Mount-AZ-SynScan-GoTo-for-Telescopes-to-5kg.html
 

You can buy them I think from here.

If the WiFi adapter plug is the same as the handset plug that came with your SynScan az goto mount, then there’s a very good chance it will work. I’d get in touch with FLO and ask.

I use the WiFi adapter on my az-eq6 using the SynScan app and it’s very good. Much better in fact than the handset IMO. You can then even use SkySafari to control your mount, all via your phone, in my case an iPhone. Very convenient.

M

6 minutes ago, johninderby said:

Oddly enough while the value of an second hand AstroPhysics refractor stays high in the US in the UK they depreciate much more. US buyers could pick up a bargain by buying a used AP scope in the UK.

yes but then you'd have to swap the steering wheel and pedals over

something I've been on the lookout for for a couple of years, for my Skymax 180: (thanks to @AndyThilo  )

My take is that it looks to me as though the secondary is a fair distance away from where it should be. One edge is deep in the light cone, and its rough-ish edge is causing all that extra diffraction. And the other side of it is way outside the light-cone,  therefore causing no diffraction at the other side. Those two extra gaps are 120 degrees apart, which suggests that 2 of the 3 mirror clips are causing them.

M

10 hours ago, markse68 said:

Had to back order but it didn’t take too long thankfully- Mars is waiting! That’s probably jinxed tonight then...

But why both?

2” for adapter and 1.25” on ep so turning ep in adapter varies the nd effect. Anyone else do this?

Very clever well done

17 minutes ago, John said:

Apologies to @Captain Magenta / Magnus for diverting this thread onto my particular issues.

Thanks again for your interesting report

Totally no apology required John, but thanks anyway. I couldn't ask more than to get the responses and input from such as you and Don - I've certainly learned a lot more than simply discovering that my Paracorr improves my view.

M

22 hours ago, JeremyS said:

Did I miss something, John? New Barlow?

Yes I was about to demand an inquiry too