Captain Scarlet

A few months ago I posted a big piece called "reverse engineering a skymax 180". Part of my purpose was to establish exactly what focal length the scope was operating at. I initially assumed one important parameter by making the assumption it was 2700mm with the supplied accessories (51mm visual back and 2" diagonal). What prompted me down that route was a similar experience to yours: it seemed to be giving me more magnification and less FoV that I was expecting.

Over the next day or so I am about to update my post, having done the extra work to exactly pin down its focal lengths, and it turns out that with the supplied accessories my 2017 Skymax 180's focal length is actually 2883mm +/- 16mm. This explains the reduced FoV and increased mag.

Cheers, Magnus

4 hours ago, andrew s said:

What I would like to know is how accurate the figure is on the mirrors as this will ultimately restrict the image quality when the seeing is good.  

It did also occur to me to ask if the secondary was center spotted to simplify collimation. If it was it would make a clear usp for them over similar clones in addition to FLO's customer service.

Regards Andrew 

I often wonder how accurate the centre spots are, especially as they're often such a key part of collimation. For a big newtonian primary it must be quite difficult to establish precisely where it is (the true optical centre, not the centre of the "slab"). For a small secondary, as long as you're prepared to remove it, it should be fairly easy to find on a hobby-sized lathe.

Fascinating. My favourite part was "There is no surviving portrait of Robert Hooke, since it is thought to have been burned by his rival, Sir Isaac Newton"

I have a canon 24-70 2.8 L lens whose autofocus has stopped working. The front filter ring has a dent in it, though I have no idea how it happened, I have certainly never dropped it. I suspect the two problems though are not unrelated.

thanks for the recommendation, I may get in touch with them...

M

rather than type out a thousand words, I’ll attach a link to my own journey starting from the exact place you’ve started:

http://www.slidingseat.net/stars/stars.html#startingout

hopefully the site works ok on your browser, seems to like a computer rather than phone though...

 the he short answer though as alluded to by @Skipper Billy is dark skies, tracking if you can, and stacked multiple exposures. 3x45s worked for me

cheers, Magnus

Nice.

I had a very nice view of Uranus tonight with my own 12" newt, a startlingly obvious disc, but it didn't occur to me to look for moons. Last night I did look quite hard for Martian Moons but couldn't see anything despite looking up where they were supposed to be. Neptune's and Uranus' moons are next on my list now. Our Moon is getting less obtrusive over the next fortnight so with luck I'll get more clear nights.

M

10 minutes ago, Stu said:

@Relpet I thought Skysafari on Android worked ok with Skywatcher Synscan mounts as you can run the Synscan app in the background provided you have enabled this to happen in the settings menu. The problem I was aware of was with iOS which does not allow background apps in the same way, so you needed two devices to make it work. This has now been fixed anyway so as far as I’m aware it works on both platforms.

Yes it has been fixed for iOS, I regularly run Skysafari pro and the synscan apps together on one iphone to control my az-eq6-plus-wifi adapter, which i believe is the same protocol as the az-gti setup

Yes I've had that exact experience too. With my Skymax 127 I looked up to see how long I had before Saturn went behind the big Magnolia, and found it'd been behind it for a good few minutes!

13 minutes ago, PeterW said:

Think I’ve got feet, legs and head sorted. Looking at coat options at the moment... just leaves the hands. The issue with observing is you’re not moving about so gloves for sport can’t be trusted to work. I got some that I now use as gardening gloves but they are a wee bit too small to keep fingers warm (totally bramble proof thiugh). 
Peter

As per @Andy0306 's suggestion, I've ordered a pair of these https://www.theheatcompany.com/en-gb/gloves/merino-liner?number=33022 .

I'm also going to steal a pair of my wife's thin woolly mittens.

I've been commuting to work by bike since the late 1980s and it took me years to solve the what-gloves-for-70minutes-when-it's-cold-and-raining problem. My only truly miserable rides were that scenario. It turns out there is no such thing as a cycling glove that's waterproof. But eventually, only quite recently, I found a pair that is completely impervious to water even for a whole 20 mile cold wet ride, but they're not cycling gloves! They were Montane trekking gloves, layered pertex, and have made such a difference!

3 hours ago, PeterW said:

 

@Captain Magenta how cold does it get down your way then...?

Peter

not too cold by temperature measure alone, but where I am there's no place with protection from a stiff cold NE wind: at 2-3 degrees with that wind I've been forced to abandon observing sessions fairly regularly due to numb fingers. Once I even had to contemplate leaving my whole rig outside overnight as I barely had the dexterity to undo the saddle-knobs to get my 12" off the mount.

29 minutes ago, Andy0306 said:

How much do you want to spend  https://www.theheatcompany.com/en-gb/gloves

 

Christ!!!!

I think the Heat 3 Special Force should just about suffice 😳

Another surprising thing that sticks in my mind is that a photon created at the centre of our Sun takes on average 200,000 years to get to the edge, I seem to remember reading...

The most important thing in Newt collimation is getting the 2 independent axes lined up and coincident: the focuser => doughnut axis; and the focuser <= doughnut axis .

The lining up of the edge of the primary with the edge of the secondary, while worthwhile, is far less serious if you don't get it quite right. By lining up the edges you're placing the secondary's edge on the edge of the primary light-cone. If you don't line the edges up, all it means is that one part of the secondary is outside the primary's converging light-cone and hence "doing no work", and the other side of the secondary is a bit too far inside the light-cone and hence missing some available converging light. It just has the effect of slightly effectively reducing your aperture and giving you slightly uneven illumination which for visual you wouldn't notice.

Summary: Fail to line up the axes properly, you get actual aberrations. Fail to line up the edges, you just miss a bit of aperture and illumination.

BTW that Gannet was about to plunge into Lough Ine in Ireland, there was one that frequented the Lough last year, a young adult I think. Lovely creatures.

Cheers, Magnus

A thing that often confuses is the fact that there seem to be lots of crosshairs around! ... actual ones and reflected ones, and the reflected ones are clearer because you can actually focus on them.

In this case what you're trying to do is align the focuser axis to bounce off the secondary and "hit" the doughnut. (the "outbound ray").

Your eye is at the centre of the focus tube. The actual crosshairs are also at the centre of the focus tube, at the other end of it, but they'll likely be a bit out of focus as they're so close. If you line up those crosshairs with the doughnut, you're guaranteed that your (centred) eye, the centre of the far end of the focus tube, and the doughnut are all in a straight line (albeit bounced off the secondary). You make these adjustments by finely turning the secondary's tilt screws.

THEN, you adjust the primary tilt to get the primary's axis (the "return ray") to coincide with the outbound, by getting the reflected (smaller and not fuzzy) crosshairs to coincide with doughnut.

I hope that makes sense

Thanks everyone, lots of options here. I hadn't realised there was such a thing as dedicated astro gloves, but applying a second's thought, given everything else that's available, of course there is! I probably won't start smoking though

M

26 minutes ago, CCD-Freak said:

Was it this one?   https://www.lightpollutionmap.info/#zoom=3.04&lat=54.3547&lon=2.7220&layers=0BFFTFFFFFFFFFFFFF

It has multiple data sets and the ability to get SQM readings for any spot you click on.

 

John Love
CCD-Freak
WD5IKX

... and use the Atlas 2015 layer for its estimate as to what best darkness to expect. 

Lightpollutionmap.info using their Atlas 2015 overlay/analysis I have found to be very accurate at two completely different sites. I spend time between SW of London, Bortle 7ish 19.05 and SW Ireland, Bortle 3ish, 21.80.

I have an SQM-L meter and have collected around 200 quite recent readings from each at various different altitudes and phases of sun and moon. At each site the Atlas 2015 estimate matches almost exactly what I have measured under best conditions, even now.

I regard that as a reliable guide as to what to expect.

Cheers, Magnus

I clear my secondary mirror of dust by using a gardener’s water spray. I fill it with distilled water, set the nozzle to “jet”, point the scope tube slightly down so the dripped-off water runs out through the front, and fire the water jet through the open focuser tube onto the secondary. Being distilled, it dries clean.

The Winter season is rapidly approaching in the N hemisphere and here in quite-dark-land I find winter nights to be some of the most sparkling and crisp. I have Uggs for my feet, thick trews and a lovely thin but incredibly warm down jacket.

But I haven’t found gloves yet that are sufficiently thin and supple to press small buttons yet warm enough to be handling aluminium objects in the cold?

What do you use?

M

16 minutes ago, RossHicksPhoto said:

Wow! Beautiful image! What lens / camera body was this using? 
I struggled to get a decent focus on my shot (above) as the clouds were rolling in fast and I was shooting by hand. 

Thanks. It was a Canon EOS 7Dmk2 with 300mm f/2.8 lens and 1.4x converter, making it 420mm f/4.0 . 1/2000s f/4.0 ISO400 was the exposure, shot as RAW. The Moon was bright enough that autofocus was fine, and it was hand-held. IIRC I used auto-exposure but under-exposed by the auto measure by a couple of stops, I find that allows the best dynamic range for images including very bright objects such as Moonshots or sunsets.

5 minutes ago, GavStar said:

... working for home all the time ... daylight hours ... solar viewing...

are you a professional solar viewer ?

Ability to see the MW immediately after stepping outside a bright room is utterly magical. You don’t even need a scope to get a mesmerizing night. So much to see and learn and recognize. As you intimate, main constellations drowned out by stars, M31 and M13 easy naked-eye objects, soooo beautiful. But when you mention this to the locals, they often have no idea what you’re talking about, that’s what it’s always been like. You only miss it when it’s not there and then it’s too late.

21 hours ago, John said:

If only it was clear !

When planets have been close to the Moon I've found them outstanding to observe.

I almost didn't bother setting up for that reason: too close, glared out. I'm glad I resisted and did set up, Mars was good. Thanks for your insight.

M

It was beautiful and clear for me last night. I spent most of the time observing through my Skymax 180 but couldn't resist at the end of the evening grabbing my DSLR/telephoto to get this, around 1am:

Cheers, Magnus