pete_l

1 hour ago, vlaiv said:

Sorry to say, but that is completely useless way to determine correct exposure length for astrophotography.

Practice beats theory every single time.

On 14/06/2022 at 20:43, Taraobservatory said:

How would you go about finding the best exposure? 

As I have always done. Take a test exposure using an educated guess of what is suitable. Adjust subsequent exposure times such that the peak of the histogram is about one-third of the way up from zero.

It doesn't matter too much if the histogram peaks at one-quarter or one-half. A "ball park" exposure time is all that is necessary.

This works no matter what camera, telescope, filters or sky quality you have.

5 hours ago, CraigT82 said:

one of these can do the job for a lot less money

I'd question that.

The one in the Amazon link plugs into AC mains power. The device in the video looks like it measures the DC current to the mount.

Something your digital multimeter will do, once you have the correct cabling for it.

New types of telescope?

One that comes to mind is amateurs starting to image more in the infra red. Primarily to beat the ever increasing scourge of (visible) light pollution.

All I can offer is non-specific advice that applies to many areas. Whether computers or not.

The first step is to strip everything down to basics. Make sure your mount has no rattles, sticky spots or loose connections. Give them a good shake. Nothing should move or disconnect.

Then connect your computer. Do the same. Wave it in the air. Turn it upside down. It has to work unconditionally. Cable-up the mount and make sure it talks to the computer 100% of the time. Wiggle the cables, check for drop-outs. Run the CPU up to 100% and convince yourself that everything is solid and continues to work.

Be aware that none of the connectors used in most budget equipment are designed for outdoor use. Nor do they stand up to unplugging frequently. They are generally cheap garbage. As are the cables!

Do slews. Do flips. Add weights and repeat. Make sure that no cables snag at any point. Add your OTA. Do all the same again. Ensure everything is tight - no slack, no play. 

Continue the same with your camera. Use the simplest possible optical path. No adapters. No filters or correctors. Satisfy yourself that the images are exactly what you expect.

Add guiding. Recheck everything and continue adding one item at a time and retesting. Then, when everything is satisfactory MAKE ABSOLUTELY NO CHANGES EVER AGAIN. 😆

I have a Borg 101mm f6.5 and it's .... nice. Though I couldn't tell you what model it is. Borg gear is a bit like IKEA. You get a collection of pieces and have to work out for yourself what goes where. As for upgrading it ... a parts number nightmare.

11 hours ago, Paz said:

I added 0.25 dioptres for better focus in the dark at infinity. This works but I think if I had gone for adding 0.5 it would have been even better.

I did the same thing, many years ago. On advice from the optician I bought a second pair with ½ dioptre more correction - just plain lenses: no varifocal or photochromic finishes.
Be aware that at night when your pupils are fully dilated, focus becomes more critical. Just like with short focal length telescopes. So it is more important that your prescription is accurate. I presume that is why eye tests are carried out in a low-light room.

Of course, for astrophotography it doesn't matter.

As rotatux says, there is some arithmetic involved.

One specification of a stepper motor is the steps per revolution number. For example, it might be 200. So with your 32 microsteps you would have to send 32*200 pulses to turn the motor's axis 1 revolution. There will almost certainly be further gear reductions after the stepper motor. You will need to find out what they are and therefore how many revolutions os the stepper axis it takes to turn your RA drive one complete revolution.

4 hours ago, vineyard said:

Is there a formula that can be used to calculate how big an image circle a particular scope would show?

I asked that question (actually: what is the image circle from your model ... ) of Meade, quite some time ago when I was considering buying a 5-figure rig from them. The sum total response from their assembled experts was that nobody knew.

I didn't continue with the purchase.

I've had a 3D printer (Geeetech A10) for about a year. What I've used it for is to print some eyepiece "bottles" and cases for electronics projects, such as Raspberry Pi boxes that need extras, such as space for backup batteries, USB  accessories and such.

I have two observations. First, if you are budget-conscious, don't forget to account for the cost of the spools of material to print.

Second is that 3D printing is mind-numbingly slow. Several hours for anything of a significant size. Coupled with my experience that it always takes me several attempts to get the print right, it quickly becomes a chore. I have also found that quite a few of the ready-to-print designs you can download don't quite work. Maybe that is due to variation between printer types, materials or even having all three axes of the printer "square".

1 hour ago, tomato said:

why don’t I see lots of images of 20+ hours

Probably because people collect sufficient data for a nice looking end result and then move on to a different target. It is, after all, a hobby. Nobody is being judged or assessed on the forensic detail of what they produce.

2 hours ago, jacko61 said:

That's the main failing of breathable membranes

Completely agree. The goal of a scope cover is to keep moisture off the scope, mount and electronics. That is irrespective whether the cover is made of fabric or is an observatory dome.

The other key function of amy sort of cover is to stop the contents from cooling to below the dew point. Since a night sky is very, very, cold, metal especially cools quickly due to radiative cooling just as an exposed windshield attracts dew and frost before one that is under a shelter.

On 27/01/2022 at 20:37, F15Rules said:

I think sitting, or lying down, is the only way to do so comfortably

I feel that one aspect which would make this research stand out from the crowd, would be to consider the needs of people of different ages and personal mobility - or joint stiffness

20 hours ago, Elp said:

never really understood the recommendation

The problem is that the world of amateur astronomy is overflowing with advice. Almost none of it is verifiable and lots of old stuff that should have been buried years ago keeps popping up.

Part of the problem is internet search algorithms that put stuff with lots of hits to the top. And the older something is, the more hits it will have.

Another issue is that almost none of the advice (particularly where mounts are concerned) is testable or quantifiable. Is mount "X" better than mount "Y"? At best this will just start a fight,  Where those who have purchased each type will wade in to its defence. Even when there is no data either for or against - apart from price, which seems to be used as a proxy for quality, or a buyer's "seriousness".

The thing about the HEQ5 is that it is the Ford Transit of mounts. It has been around for a long time. It has sold very many. Even if there are mounts that are "better", it is at least a known quantity. The safe option.

I am sure that there are now better mounts. If only someone could come up with an objective measure of goodness. One that everybody agreed with (see above about people defending what they have already purchased) and that could be publicised without suppliers threatening to pull their advertisements (or not send "influencers" free stuff) if unfavourable reviews were made.

On 17/01/2022 at 18:02, mikemabel said:

I have a heq5 pro mount which i am finding increasingly hard to move and setup

Have you considered a dolly?

In case that is a term limited to British culture, I mean something like this:

On 15/01/2022 at 21:18, dazzystar said:

either the Beelink U59 or Mele Quieter2 mini PC

I am not a (nearly said "fan") admirer of PCs with moving parts for outside use. I believe the Mele does not have a fan. I'd go with that.

9 hours ago, Giles_B said:

the bar only needs to hold about 600g in weight

In that case why not make one from wood?

If you know someone with a table saw they can cut the angles correctly and you can have the bar whatever length you desire. Plus mounting holes (untapped) where ever you please.

If you worry that it will get indentations from fixing screws being too tight, put some sheet metal sides on it. Or use a hardwood such as oak.

16 hours ago, Quetzalcoatl72 said:

my rc8"  ... the stars are always zigzagged across the screen.

Presuming you have got the scope+mount balanced in all three axes, then something is loose.

All you can do is go over everything, even those things that are impossible, and give them a good rattle. Then tighten it all and remember that when out in the cold, stuff gets loose again.

On 25/12/2021 at 04:54, eshy76 said:

And all this in a mount weighing a backache killing 5kg (my RST-135 is actually 3kg!).

Is that really much of a benefit when a person would load the mount with up to 20kg of other equipment? It isn't as if you'd attach everything to it and then carry the whole thing to its place of use.
I see a mount as one component of a system. As such it is difficult to see what benefits this contributes, that a more mainstream mount would not be able to do for a similar price.

14 hours ago, StarryEyed said:

all the mounts coming out of the factory should be performing as your's does

Yes. However, mounts do not perform in isolation.

The OP tells us they have a 3kg OTA plus what seems to be a DSLR on a mount that is rated for 20kg. The focal length (432mm) is also very forgiving.

From the press release:

Sony says. “By increasing amp transistor size, Sony succeeded in substantially reducing the noise to which nighttime and other dark-location images are prone.”

So for astro use, the main benefit is lower noise. Does that mean non-cooled cameras will produce better results? Hopefully. Does it mean we can dispense with cooling? Probably not.

However, the main thrust of this development seems to be the tiny little sensors used in phones. Whether the technology will feed through to decently sized sensors is unknown.

34 minutes ago, dazzystar said:

What would be there minimum specs I should be considering

I would suggest that all you need is a cheap'n'cheerful second-hand laptop.
Things to consider would be the number and type of USB port.

2 hours ago, Rusted said:

Any <cough> constructive ideas on the "rear guards" purpose?

My 20 year old Scheppach capas3 compound mitre saw doesn't have such a thing.
Could it be a marketing "feature" perhaps?

On 19/11/2021 at 18:45, UKDiver said:

A lot of the Svbony kit on their Amazon site is 20% off for Prime members/Black Friday deals.

I just looked at the amazon link for the 18mm. Then I found the same EP on Amazon Spain (being as how that's where I am )

Just substituting ".es" instead of ".co.uk" on the web page shows quite an interesting result. Even without accounting for the £ - € exchange rate.

On 26/10/2021 at 23:28, Simon M said:

What would you spend your money on? 

Well, what I would spend your money on would be:

EQ8 head (4k), PrimaLuce C120 pier (1k), 100mm photoline refractor (2k), ASI183 colour camera (1k) or ASI183 mono + filters (2.5k), and another 1k or thereabouts for a computer, off-axis guider+cam and other bits'n'bobs.

The cheaper version would swap the EQ8 for a CEM70 (3k), the C120 pier for a C82 (500) and stay with an OSC camera.