[Grant Privett]

I looked at the focusing knob on my C14 and, also, pictures of older C14s and noticed that only mine has a thin long bolt coming out of the top of them and, also, a wider addition. The layer of cork between the addition and what may be the original is suggestive – for locking?

I’m wondering if the bolt stops the focus knob being wound fully clockwise. Will have a look tomorrow – I need to rebalance the scope anyway and the weather should be good.

EDIT: Work stopped me getting out and testing the scope before dark and now its rain through until Saturday….

• This reply was modified 2 weeks, 2 days ago by Grant Privett.
• This reply was modified 2 weeks, 2 days ago by Grant Privett.
• This reply was modified 2 weeks, 1 day ago by Grant Privett.

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[Grant Privett]

Hi Ian,

Yeah, thats roughly what I hoped to do, but I found that when I hung the CCD on the focuser, even when the focuser is set at its furthest from the OTA, the Moon comes to focus way beyond the CCD – hence the need for lots of adaptor tubes. 🙂

Inevitably, I didn’t find this out until I had run the focuser across its full 3″ range in 1/8″ jumps looking for star images at each position. I was so convinced it should work that I did it twice with different exposures. Saw a couple of bright stars travel through – while filling 25% of the screen – none anywhere near in focus.

So, that was 2 clear nights wasted as at -4C I wasn’t sitting out there for more than 2 hours at a time.

More after I have a look inside the Moonlite…

EDIT: No glassware found in the Moonlite. Now wondering why the focus knob was modified…

Grant

• This reply was modified 2 weeks, 2 days ago by Grant Privett.

[Grant Privett]

Yeah, I’m confused/concerned, but having never owned an SCT before, I assumed that I was being dumb and missing something obvious.

The OTA previously belonged to Ron Arbour. He said he had obtained after it was stored in a garage that flooded – I think that is what was said – it was a long time ago and in passing, as we were actually talking about some automated image alignment software I had written for him.

He clearly did a nice job as the mirror is pristine and the inside of the tube looks good too. The focuser works fine as well. I don’t recall seeing another C14 there, but there might have been.

Will dismantle further this afternoon and am really hoping I find a lens in there…

[Grant Privett]

Thanks for replying Nick. Thanks for the info on the direction of rotation.

There is a focus knob replacement + two clampable rods at 120 deg intervals from the knob round the main axis. I wound the focus knob fully clockwise and got a distance from scope body to an image of the Moon on a piece of card of approximately 310mm. Then I wound it fully anticlockwise and the focal point went out to more than 600mm – the dome wall got in the way of precise determination.

At best then the focal point is 310mm beyond the back of rhe scope body – which is approximately twice what I have heard reported on Cloudy Nights before. I’m not using a diagonal, so it looks like a long way – does that sound right to you?

I’m going to take the Moonlite to pieces in the light tomorrow as I’m beginning to wonder if theres a Barlow lens or something in there rather than a focal reducer. Good for planets…

Pic of the scope focuser when it was indoors attached.

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[Grant Privett]

Try Photoguard?

I imagine they will want to know where you are leaving it. Theres a lot of difference between a front garden in Tottenham and the backgarden of an isolated cottage on The Fens.

• This reply was modified 1 month ago by Grant Privett.

[Grant Privett]

Tim,

I know nothing about NINA but wondered what the problem is with updating ASCOM to v7.1?

Grant

[Grant Privett]

I’m unclear. When you say: “although meteor analysts tell us not to expect meteor storms such as in 1999, etc.” do you mean this year or in 2031?

[Grant Privett]

Hell, that is outrageously good and the stuff at the dim end of the tail must be seriously dim. Its a lovely piece of work.

So what are they doing that everyone else isn’t?

Can I assume they take superb flatfields, remove the stars, remove sky gradients and then work on the tail with a very non-linear stretch and noise suppression before draping it back on one of the original images?

Perhaps they takes the longer exposures to catch enough signal from the sky (that the tail is similar in brigtness to) so when they subtract the sky theres enough signal left to avoid it being horrible grainy.

I sort of assumed they did short exposures for the bright in-close fine detail and long exposures for the extended tail…

Sneaky is best and all that.

• This reply was modified 2 months, 3 weeks ago by Grant Privett.

[Grant Privett]

I eventually beat MS Teams into submission and I’ve sent out invitations to all those who responded to my gjprivett@dstl.gov.uk email address.

Please note: I shall be reading my emails up until Saturday night, so anyone still wanting to join in, can contact me.

I will send the pdf out to those who expressed an interest, whether they attended or not as weekends seem pretty busy in most households. 🙂

See you all on Sunday morning.

[Grant Privett]

I think its done in recognition of the fact that people who live in cities are frightened of the dark.

They associate it with danger.

Which is weird, as a Home Office study in the 90s found that if you turned down street lighting in an area the crime rate dropped.

Also, the report is odd. Why are the mags referred to as 16:00 and 22:00 and not 16.0 and 22.0? Didn’t anyone proof read it? Almost as if the author confused sky brightness with times. Hopefully, no AIs were involved in the authorship.

Also interesting that the sky brightness value for E0 changed in 2019. In which direction?

[Grant Privett]

Thanks for the plots. Already looking forward to it!

At the time its in Bootes. Good timing for T CrB to finally go bang.

[Grant Privett]

The eclipse that Google denied would be visible from Salisbury, viewed from near Salisbury…

• This reply was modified 4 months, 2 weeks ago by Grant Privett.

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[Grant Privett]

Oh, I don’t know. I think I joined for the first time when I was 12.

Lead counterweights were quite common then. My 4″ Newtonian had one.

I’m really not sure when I grew up enough to assess risks accurately and mitigate them. Brain development is supposed to stop at about 24 isn’t it? 🙂

[Grant Privett]

Yes, I have 2 weights and a 5kg – a conversion job.

The fun is that I want to use it with a 1980s C14, which is hefty and… its got a somewhat over engineered (15kg) cradle holding it. So, with focuser we’re looking at >35.5kg load. I know its on the edge for balance but certainly will be if I add something like a filter wheel and OAG. I have to say I’m tempted to stay with the current counterweights and extend the counterweight arm – though playing with molten lead again would be fun.

As for all this talk of molten metals: don’t try this at home kids.

• This reply was modified 5 months ago by Grant Privett. Reason: Safety Notice!

[Grant Privett]

Thanks to everyone for their suggestions. I have to say the leadwork looks really nice. Very neat – and probably even better after Hammerite. The sort of thing I would have rushed to do as a teenager. 🙂

Am kind of leaning toward the Olympic weights though. I wondered about stainless versions but they are more expensive – as you might expect. So something cast iron seems the best bet with an extra coating of paint and possibly one of these (see below) araldited to the inside to avoid it shaking about + velcro as Robin suggested.

https://www.lsengineers.co.uk/excavator-bucket-bush-i-d-25mm-o-d-33mm-length-30mm-200-945.html?utm_source=google&utm_medium=cpc&utm_campaign=google-ps&gad_source=1&gad_campaignid=17427838553&gbraid=0AAAAADr__mm9v9ZUrF6P2OozSHWWtxTOB&gclid=Cj0KCQjwzaXFBhDlARIsAFPv-u83vjU5_P-rDQ9z8awbLTjtUTA7Ki41NeQPFh2hei1wcGPZM16rFXsaAlV8EALw_wcB

A shame that no astro engineering company offers lathed rings to allow the conversion of weights for Paramounts and other makes.

[Grant Privett]

My options appear to be:

1, additional counterweights – £400 for 9kg
2, replace the cradle for one lighter (its very robust) – $560
3, modify stainless steel 10kg Olympic weights – ~£300
4, extension shaft for counterweight arm/rod – £135

I know which one I’m gravitating toward…

[Grant Privett]

Yeah, I noticed someone on Cloudy Nights took that approach. But its 50 years since I messed about with molten lead. Will give that some thought.

I saw a Software Bisque weight on line at £401. Eek!

Tempted to get a weightlifting weight (2″ bore) and try to put a mild steel collar of some sort in that – even I could run one up on a lathe.

• This reply was modified 5 months ago by Grant Privett.

[Grant Privett]

I love the 112 authors not listed. How many words is that per author?

Is this going to happen whenever the LSST consortium publish?

[Grant Privett]

I would say that, ideally a flat is needed for lunar and planetary observing.

Yes, stacking will help to hide any dust doughnuts present and – depending on how the stacking is done – even vignetting, but the final result will normally be better if flatfielding is done.

And don’t forget that flat frames need their own darks, even with CMOS sensors – as bias offsets may be present in the image.

[Grant Privett]

So, if you give ASTAP an ephemeris created by (say) JPL Horizons it align multiple images to keep the comet images stacked? Sounds nice.

I see it runs under Windows and Linux – under Linux it could use Astrometry.net for platesolving. How is it doing it under Windows – using the comet’s predicted RA/Dec as the centre to search for star patterns? Plus possibly a hint at sensor pixels size and system focal length?

How do you find it to use?

[Author]

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