Captain Scarlet

I have 3 baader diamond steeltracks. 2 on newts and one on my skymax 180. As John says, they are superb, much better than the DS upgrade. Another decent alternative is the Lacerta DS upgrade to the stock unit. I had one of those too.

But you will need to drill 4 new holes in your tube to fit the steeltrack. Baader’s instructions say the mounting plate fits skywatcher holes but they’re wrong. It’s not difficult though, use the detachable mounting plate as a template. Thereafter there’s lots of room for mounting adjustment.

good luck, Magnus

I’ve been asked on occasion when I’ve shown people the streak of the Milky Way, and that it’s “our” galaxy, why does it not look anything like galaxies whose pictures they’ve seen on Hubble?

I reply by saying that it’s like looking at a tree. It looks quite different when you’re inside looking up than when it’s a familiar object a few hundred meters away.

I got my neighbour in the UK into astronomy by showing him Venus during the day. He now regularly uses it as a party trick to amaze his friends.

I like to think that 4-odd years into this absorbing pastime, I know my way around the Northern sky reasonably well. If shown, I can recognize most of the major constellations or their defining asterisms. I can even draw most of them, and I'd be able to point them out to a newbie saying "see that, that's a Swan" or "that looks like a warrior with a bow". Etc Etc.

Examples of this "easy to recognize and recall" category, in the order in which they appear in my head, are for instance:

Orion (looks like a hunter with a bow); Leo (looks like a legged beast); Cygnus (looks like a swan in flight); Ursa Major (looks like, er, a saucepan nonetheless extremely recognizable); Ursa Minor (another saucepan); Taurus (a bull's head); Triangulum (a square circle triangle); Delphinus (does look like a dolphin); Aquila (open-winged eagle); Lyra (harp-shaped); Pegasus (OK not much like a horse, but that great square is easily recognized. Even if one of its main stars isn't actually officially in Pegasus); Cassiopeia (big W); Gemini (two standing figures); the list goes on.

The point is, however much they may or may not look like their name, all these shapes are quite recognizable.

But, in my opinion, there is one glaring exception to the recognizability rule: ANDROMEDA. No matter how much I look at Andromeda, I just cannot "turn" it into a memorable shape; nor would I recognize it if someone drew it out for me.

Anyone else have any similar mental blocks?

Cheers (light-heartedly frustrated at having just had to drag all my kit back in again when clouds refused to dissipate as the forecast ordered them to)

Magnus

The past few days have seen some lovely clear nights, but this no-Moon season the prevailing weather has scuppered any chance of being able to set up any sort of scope. Said weather has comprised clear sky and sunshine (or stars), interspersed every hour or so with a sudden violent heavy rain-squall. And generally very windy.

Last night was better than most, but I had still not been allowed an opportunity during the evening to set anything up, and by the time it looked “set clear” it was too late and I was too tired for anything other than a binoculars session. But it turned out to be a nice one nonetheless, if short.

Aside from cruising the Milky Way from Cassiopeia to Cygnus, these are the moments I remember:

Nova Cas - I started by looking for the Nova in Cassiopeia, which for the first time in many views, I gave up trying after failing to find it. Mainly because my guiding-points, Shedar and Caph, were almost exactly at zenith, and following their line to M52 required me, literally, to bend over backwards. My binoculars of choice were Zeiss Conquest HD 15x56, i.e. quite big and heavy, and my patience and back wore out before I properly found my bearings. So I gave up on Nova Cas.

M31 - Once my eyes got adapted to the (21.57) darkness, I noted that M31 was easily direct-naked-eye. And through the bins a dust lane was evident, as were M110 and M32.

M33 - I moved down to M33, and couldn’t quite decide whether it was perhaps not just-about naked eye detectable. Through the binoculars, though, it was quite bright, with a hint of spirality.

Square of Pegasus - I was now facing, more or less, the Square of Pegasus, so I decided to try to count how many stars I could see naked eye. I eschewed the bins for this, as I didn’t want to prejudice my imagination. I counted 10 definites, and with averted vision there were coming-and-going hints of a handful more. Based on the definites, that puts NELM for my eyesight just over 6.0 taking account of atmospheric extinction.

MW's Shadow - I also remembered reading that in darkness such as this, the Milky Way ought to cast a shadow. So I put one hand above the other separated by perhaps 2-3 inches, and sure enough there was a shadow, and it moved when I moved my hand. Extraordinary! Testament not just to the lovely skies I’m lucky enough to have, but to the incredible range and sensitivity of our eyes!

M101 vs M33 - Turning around, and with M33 still in memory, I looked for M101. To begin with, I was looking in completely the wrong place, thinking it was 10-20 degrees North-ish of Mizar/Alcor. Obviously I couldn’t find it so I had to look it up. In fact, it’s much closer to Ursa Major’s saucepan-handle. It makes a more-or-less equilateral triangle with Mizar and Alkaid, only 5-6 degrees North-West of each and “halfway in between”. Once I knew where it was, I found M101 straight away, and I can report that it was MUCH dimmer than M33. Partly, that was down to atmospheric extinction, which by my formula would have reduced M101 by about 0.5 magnitudes more than M33’s extinction, on an already rather faint extended object. I also tried to find M51, but that was getting far too close to my Northern horizon and I couldn’t see it.

M13 & M57 - Finally I tried for M13, which is normally naked eye out here, but at only 20 degrees above my most light-polluted horizon last night I couldn’t see it without the bins. With the bins, of course, it was there. Finally-finally I tried for M57, the Ring Nebula, and although I definitely think I was seeing it, through the bins at only 15x times and hand-held (i.e. not perfectly steady platform), I couldn’t distinguish its “ring-ness” from that of neighbouring stars.

That was that, a short session but some things I hadn’t tried before and always a joy to stand under skies like this.

Cheers, Magnus

I love MW images vertically through trees and these are lovely. ESP with M31 in shot. Very close to where my father-in-law lives too.

M

Lovely.

I was just reading this and thinking OK I need to go outside with my own bins and do a similar session, and literally as soon as I thought that, rain started drilling on my windows.

That’s what the weather has been like these last few days. Alternating blue sky / heavy rain every 45 minutes during the day, the same at night. I just went out to look at the obvious Milky Way, and now 10 minutes later it’s pouring. No chance of preparing a scope session.

Magnus

And how about that glaring gap at 12” Stu? I know you have something up your sleeve there…

M

PS I just came back from eating out and arriving home the sky was beautifully clear. Skipping inside to grab some binoculars, when I stepped back outside it was clouded over and raining. Space of 60 seconds!

Between where I use my scopes and where they live there is a sliding almost-all-glass door. Last year whilst setting up in the dark I charged back inside to collect the next bit of kit to take outside, forgetting that I’d closed the door after the previous trip. I walked straight into the glass and broke my nose. The scratch on the door-glass where my glasses hit it is still there as a reminder.

Magnus

It’s just gone clear between squalls so I thought I’d get a quick look before bed. Through 15x56 bins. It looks very much the same as the bright star in M52, SAO 20606, making by my estimation around 8.2 mag. 

Magnus

Pouring rain where I am.

But I can’t resist asking. What’s the red bag for?

M

Re Rigel I'd put it the other way around. If Rigel is proving difficult, you have no chance at the Pup. But as said, Rigel is quite easy. I have not yet seen the Pup, despite having tried a lot. My path has usually been: Rigel => E & F in the Trapezium => Pup (attempt). Last Orion-season I could usually see the E & F, but on the occasions the E & F were really clear, I still never managed Sirius B. Needless to say, I'm looking forward to resuming my attempts.

Cheers, Magnus

10 hours ago, johninderby said:

Or the Geoptik Nadira chair  Similar quality to the Berlebach

https://stargazerslounge.com/topic/282520-geoptik-nadira-observing-chair/

I added a leather seat to mine.

I wonder is it feasible to put the seat into the top slot?

45 minutes ago, Stu said:

Magnus, I’m shocked. You already have a very fine observing chair…… 🤣🤣

Indeed! And from a functional point of view there’s nothing wrong with it. But when I came over here there wasn’t enough room in the car for it. Until I can get it over here, a Geoptik or Berlebach will have to serve in the interim 🤣

I'm under pressure to supply a "present-link" for my upcoming wedding anniversary, or risking getting something I'll have to pretend I like. In spite of owning an enviable array of astro-stuff, I still find myself balancing, bending or stooping in various uncomfortable poses. A glaring void in my stuff-list is, therefore, an observing chair. As a self-confessed Berlebach junkie, I have to ask: Charon, Hydra II or NIX II?

Opinions, experiences and recommendations, please.

Yours, Magnus.

1 hour ago, jetstream said:

… if seeing limits magnification so much maybe these expensive scopes arent worth the time?

I completely agree. But to save the terrible shame of scrapping these scopes, on reflection, actually make that refraction, I think it’s probably best to send them to me.

Nice read.

Saturn Nebula on my list. I’m pretty sure it’s been on a few of my lists but my observing is not terribly well organized and I have yet to see it.

M

The lightpollutionmap.info website has a drop-down menu where you can select the dataset. Most are VIIRS 20xx , which are “how bright it is” from the viewpoint of the satellite. IE top-down. But one, the Atlas 2015, is a modelled “bottom-up” dataset based on the then most recent VIIRS data. IE it’s what darkness is expected to be like for we, the observers.

Although it’s based on 2014/15 data, I have found it to be pretty good, even perhaps a slight underestimate of how dark it can get. I have approximately 500 points of SQM-L data from the last couple of years from two very differently bright locations. One is near London, which generally gets true best readings of 19.15 from my SQM-L. The website suggests 19.05.

The other location for which I have data is here in SW Ireland, which is 21.80 according to the website. I have recorded 22.0 on occasion.

Cheers, Magnus

If you detach the mirror cell and the spider you could probably get both in? 😄

31 minutes ago, Sunshine said:

A certified planet killer, I had the 150 though they do take their time cooling. That 180 must take a good 1.5 hrs to equalize, I must say I’m a little smitten with your mount, what mount is it? it looks great!.

The mount is an AOK AYO ii, which I bought off here and sent off to AOK to get encoders fitted so I could use it with my Nexus DSC. Plus AOK's optional extra handle. It works well. Luckily my Skywatcher AZ-EQ6 extension bar fits the AYO ii's hole.

I got my skymax 180 out last night for the first time in 3 months or so. I do like this scope. Although the seeing was as bad as I think I’ve ever seen. Jupiter Saturn and the moon were fizzing wobbly blobs. Not worthy of an observing report I thought I’d put a couple of pics up here instead.

1 hour ago, kbrown said:

... Also your L1 + L2 + Holder Diameter does not add up to the major axis of my secondary => 21.28mm + 35.28mm + 35mm = 91.56mm while the actual major axis of my secondary is 106mm. I'm attaching a spreadsheet I made based on the above article.

 

Cheers,

Kari

secondary_mirror_offset.ods 89.72 kB · 0 downloads

Re adding up the components you need to multiply the holder diameter by sqrt 2 to make up the major axis length, because the holder is at 45 degs to the back of the mirror

i.e. my method's values: 21.28mm + 35.28mm + 35x1.414mm = 106.05mm

but that website's quoted values for L1 and L2, when added to the oblique length of the secondary, do not add up to 106

i.e. 29.89 + 41.11 + 35x1.414 = 120.49mm

Perhaps the website is not returning L1 and L2 as I have defined them, but some other dimensions? I can't check as I can't open your spreadsheet, it's a format my computer doesn't recognize, so I don't know what input values you've used: i.e. distance of mirror-interception from focus etc.

Cheers, Magnus

So, finally, a worked-through example. I’ll use values from my own customized Newtonian

“s”  = 309mm optical bounce point to focus
“d” = 32mm diameter of holder for esondary mirror
“M” = 70mm minor diameter of secondary mirror
“t” = 0.7mm thickness of adhesive tape

First we need to compute “A” and “B” as per the preliminary formula
A = 0.5 * (s + M - sqrt(s^2 + M^2))
A = 0.5 * (309 + 70 - sqrt(309*309 + 70*70))
A = 0.5 * (309 + 70 - sqrt(100,381))
A = 0.5 * (309 + 70 - 316.830) = 0.5 * 62.170
thus A = 31.085mm

Now we can compute “B” as per our other preliminary formula
B = M – A
B = 70 – 31.085
thus B = 38.915mm

Now we have enough to achieve our goal of determining L1 and L2 so we know exactly where to mark the back of the mirror for placement:

L1 = (A – d/2 –t) . sqrt(2)
L1 = (31.085 – 32/2 – 0.7)*1.414
L1 = (31.085 – 16 – 0.7)*1.414
thus L1 = 20.34mm

similarly
L2 = (B – d/2 + t) . sqrt(2)
L2 = (38.915 – 16 + 0.7)*1.414
thus L2 = 33.39mm

according to the labels in the following diagram:

I hope that's been helpful, and that you get your mirror attached safely!

Cheers, Magnus

I have a Kowa spotting scope, 88mm aperture and 510mm focal length, so quite nice for wide field viewing. Kowa do a special 1.25” adapter which allows astro eyepieces to be used. I have one of these adapters, and when I returned to Ireland a couple of months ago I wanted to use it but could I find it? Oh no.

After literally hours of searching, I eventually found it, still attached to one of my eyepieces where I’d last used it 🤦.

... worked example still to come ... I've attached an Excel spreadsheet which allows you to calculate it.

I'll do a worked example in text format too

Cheers, Magnus

SecondaryMirrorCalculator_SGL.xlsx