Cosmic Geoff

4 hours ago, Steve Reed said:

Would a standard laptop charger offering 12v and 5A

My laptop chargers deliver 19 volts. 

There are many sensible options - either a rechargeable battery or a mains powered regulated PSU.  Whatever you use, it must deliver at least +12v to 13.8v and be capable of delivering several amps.  I mostly use a multifunction car engine starter, or a Celestron LiFePo battery pack.

The car starter can inflate my car tyres as well as running my GoTo scopes.  The Celestron power pack also acts as a useful work light and has USB power sockets.

The two ends should look the same as regards wire order.  I guess that without a good cable to compare with, you can't tell how it should be reassembled.

28 minutes ago, The60mmKid said:

It requires occasional collimation, thermal acclimation before use, possibly dew management,

Maks rarely if ever require collimation. I have not had to touch mine even after several years of ownership.  The design has been used for gunsights on tanks, which suggests a certain robustness. 🙂 

Even quality refractors can be collimated, if you are determined to tinker. 

Maks DO require a dew shield.  Refractors also require a dew shield, but they mostly have one built-in and less conspicuous.

If FLO are offering you a customer return Mak, buy it quick before it goes out of stock. I'm sure it will perform exactly the same as a new one.  A no-brainer unless you have a fetish about pristine packaging or clamp marks on the dovetail.

Depends on the retailer. FLO only sell new, and sometimes sell customer returns which are fully refurbished, checked and as-new, AFAIK.

Other retailers selling second-hand astro equipment may provide gear that they have not checked and tested. I bought a used SCT from a certain company for an attractive price. The seller pointed out that it had superficial scuffs and dents. I found that it was well out of collimation, and the power plug was making poor contact, causing erratic failure of the GoTo.  Rather than launch a complaints procedure, it seemed less bother to set-to and fix the problems.  Since then, the scope has performed as well as a new one.  But if I had been a clueless newbie, I would probably have ended up trying to return the scope. for a refund.

In conclusion, if you don't have a clue how to fix or adjust a telescope, don't buy one that might require attention.  Also be aware that there is not much that can go wrong with a telescope in the way of in-service failure, other than the electronics.  The chances of the electronics failing at some time are the same whether the scope is new or used, but if it is under warranty at least you have a come-back.

I had issues with one mount which required re-loading of the mount firmware to restore it to operation.  This required a certain familiarity with adapters and computer operation on my part, otherwise it would have meant an expensive encounter with a specialist repairer. 

Lesson 2: don't buy a GoTo model unless you are confident with computer operations. 

Another trial effort with my 127mm Mak, ASI462MC, and Astromania UV filter and other filters.

I got a UV image in mid-afternoon with an exposure of around 7ms and a satisfactory frame rate.  These are all from a 5000 frame video, cropped and centered in PIPP.  Visual exposure time ~0.06ms, IR exposure time ~0.15ms, so the UV exposure is 100 or 50 times longer.

While I got an UV image, it isn't very good.  The sky background was much brighter on the laptop screen than it appears here.

Interesting discussion here: https://www.cloudynights.com/topic/849249-are-newts-better-uvch4-planetary-imagers/

Among other things, a Classic Cassegrain should work well, and blue filters might show something if your scope has glass.

Bad news on this topic for SCT owners: https://www.researchgate.net/figure/Transmission-for-an-8-Celestron-SCT-Schmidt-corrector-plate-coated-with-Celestrons_fig3_241553344#:~:text=In-house transmissivity tests on a modern Celestron 8",H and J-bands was about 74% on average.  Steep dropoff below 400nm.

People used to make their own Newtonian telescopes when I was a boy, but nobody, except hobbyists who want a Project, does this anymore. 

In most markets it is cheaper to buy a used telescope than to buy parts to make your own.

Beware of reviews written by people (e.g. shoppers on Amazon) who know little about telescopes.

14 hours ago, Pete Presland said:

I think my corrector plate blocks some of the signal, but obviously i have nearly twice your aperture. 

What time did you capture at?

Image above captured on 15th at 20:58 to 21:13 UT, exposure 425ms. (127mm Mak)

A test with the same kit the next afternoon, with Venus near the meridian, gave an exposure of ~35ms, and without the diagonal and ADC more like 9.4ms (times so much shorter that I thought something had gone wrong somewhere).

A test the same evening, with a 203mm SCT at around 21:30  UT and  thin cloud about, gave an exposure time of ~900 ms, without diagonal or ADC, so clearly not worth trying to take an image video.

I would like to try again with Venus near the meridian, but conditions have not been suitable, and I also need a means of aligning the SCT in daylight.

My experiments indicate that eliminating the prism diagonal and the ADC has some beneficial effect on the UV exposure rate.  I also found indications that the time of day (altitude) had a significant effect.

To support the latter, charts indicate some attenuation of UVA at zenith, and if one looks up "air mass coefficient" it can be seen that the path through the air increases with increasing zenith distance.  At least one Venus imager reported improved results with daytime imaging.

Kon - your series of images looks great.

It seems that my Astromania filter is not the problem. I will try eliminating glass (eg prism diagonal & ADC) from the optical path of my Mak and 8" SCT  and see if that helps at all.

Some digging reveals that the ASI462MC  could have a relative response of 0.1 to 0.2 in the near UV,  the other (more expensive) UV pass filters have a relative response of 80% at around 320-380nm, and as for optical glass, it varies.  Some pass near UV while others act as an effective UV-cut filter.

Seeing the curves, one wonders why anybody would want to spend money on a UV-cut filter for any gear with glass elements...

I received the Astromania budget 3-filter set today and this evening tried it out with my 127mm Mak.  Full setup:  127mm Celestron Mak,  Circle T prism diagonal, filter wheel, ADC, ASI462MC.  Video of 2000 frames.

I found that the exposure time with the UV filter was astoundingly long at around 460ms (2.4 frames/sec. 

Compare with visual band: 0.2ms, IR 0.4ms, and just for comparison, not imaged: OIII 7.8ms, methane 7.8ms.

I wonder if it is the UV filter or the sundry other components that causes the low sensitivity.   The ASI462MC camera is probably not ideal for this role but I expected better.

The ASI183MC appears to have a significant IR response (though the spec does not show the response beyond 700nm) I would recommend using an UV/IR filter.  ZWO offer one for around £25 which I have used successfully with other of their cameras.

Other ZWO cameras come with a fisheye lens, which I have found mainly useful for demonstrating the funny colours you get if you don't fit an IR-cut filter.  You could experiment with aiming your outfit at treetops in daylight.

I had a look through the front of my 127mm Mak (now several years old) under a strong light this morning, and could see white specks of dust apparently on the large (main) mirror.  These clearly do not affect the operation and I do not intend to do anything about it.  I am reminded of some previous threads in which newbies are advised not to shine a strong light into their telescope lest it reveal anxiety-inducing dust that does not affect the telescope operation.

13 hours ago, Kenneth Spackman said:

there is a lot of dust particles and a piece of swarf or something on the secondary mirror.

The secondary mirror surface consists of an aluminised area in the middle of the corrector lens and cannot be seen by the user.

Be careful what you ask for when requesting a refund or exchange.  As noted above, there may be a limited period for a no-fault return, and if you claim there is a fault, the seller may dispute this or let you wait a few months while it is sent back to China for examination. Do you want an exchange Mak with the same focus mechanism that you clearly don't like?

BTW, some owners fit refractor-style focus assemblies to the back of their SCTs or IIRC, their Maks.

You WILL need to refocus on changing eyepieces, unless the eyepieces are parfocal.  There shouldn't be any visible dust or swarf inside, but this will not in practice affect the performance. (Just consider, there is a darn big secondary mirror blocking part of the aperture). 

Yes, the focus does require some winding, but not a whole lot. Maybe your other scopes had a different character of focus mechanism. 

You are entitled to a refund if the telescope is in fact faulty.  From your account, either the seller is being difficult, or he hopes that once you have got used to the telescope you will accept it as OK and stop complaining.

As a declaration of interest, I have a 127mm Maksutov, essentially the same instrument as yours, and I am extremely satisfied with it.

Who is 'a well known seller on the internet'?  Was this a specialist astro retailer, or some other large group known for piling it high and selling it cheap, along with bad customer support?

Yes, the quality of the Skywatcher products leaves something to be desired, if one accepts all the complaints. But you get what you pay for. Is there anything cheaper or as cheap as the Skywatcher kit that is better made? I don't think so.  If you think the product is really unacceptable, you have the option of returning it under warranty.

I have seen beautifully made mounts at astro shows, but with eye-watering price tags.  

In the same vein, if you wanted a premium quality car, what would you buy? A Merc or BMW, or the cheapest marque on the forecourt? 

I have some Skywatcher products. They didn't cost a fortune, and they work.

1 hour ago, gold682 said:

- a battery pack of some kind?

- a replacement for the 10mm eyepiece and/or a complimentary eyepiece (zoom?)

- replace red dot finder with the skywatcher RACI? 

Battery pack is needed. Don't even think of using internal AA cells (etc)

Replace the 10mm eyepiece with something decent.

Red dot finder may be OK. Your choice whether you get a straight-thru or RACI finder instead.

Any historic interest here? There was no interest in this in the For Sale section.

The GPS is more useful if you use the Goto mount at multiple locations.  Otherwise it just sets the time for you, which is handy but perhaps not worth a significant expenditure if you normally wear a watch.

The Starsense saves the faff of doing the alignment, but you still have to set the time (unless you can persuade Starsense and GPS or a phone or tablet to work together).

Both the Skymax and the DX5 telescopes are available with various alternative mounts.  For the beginner, the SCT as applied in the DX5 is a tried and tested design not too different in characteristics to the Mak.   Both designs being long focal length, narrow field instruments will benefit from a sophisticated mount that holds the telescope steady, tracks and finds stuff in the murky unban or semi-urban skies that most amateurs have to contend with.

GoTo is great, but seems to baffle some people not of a technical bent.🙂 If you decide on the Skymax GoTo (or any other) don't even think of running it on the internal AA batteries - get a proper power unit, eg a astro power tank, or a car engine starter (basically the same kind of thing but not badged for astro use).

Somebody will probably suggest yet more telescopes for you to consider. Whatever you decide on, don't agonise over it too long, as the chances are that whatever you buy, sooner or later if bitten by the astronomy bug you will upgrade to a bigger or more specialised instrument (or even several 🙂).

So why would it need a delrin disk there and why is it missing?

Writing as a mechanical engineer, I would say it would have a gasket there to take up any irregularity in the flat machined surfaces. If you can't find a gasket of suitable diameter on ebay, you could make your own of some suitable material.

28 minutes ago, MrChris said:

I’m new to this and on setting up the nexstar 6SE I found ‘Zambia’ (not surprisingly) isn’t on the list of locations. If I input longitude and latitude, will that suffice? 

Setting longitude and latitude should be more accurate than setting the nearest city (or country). The 'nearest city' option is provided for the convenience of users, making it easier to enter something close to the actual location without error.

5 hours ago, Chickpea said:

If I only use current limiting, rather than OCP, is there still a need to provide the higher current (8A - 10A) for start up? Would the capacitors still charge if only 4A is provided?

If you use current limiting, I think that will be totally fine. If you limit the switch-on inrush current, that should be totally fine and the capacitors will still charge - just taking a few milliseconds longer.

So long as you power your mount with the right voltage connected the right way round, and with sufficient current capacity, with adequate power leads, nothing should go wrong.

Many of us power our mounts from a battery with no protection other than a fuse and don't have problems.

If you put your scope in the Home position, you should be able to see Polaris in the finderscope, if not in the main telescope.  A red-dot finder works well here, as you can easily see how far you are off, assuming the red-dot finder is aligned to the main telescope. 

Polaris may be the only star visible in the polarscope, when it is in focus.  Once you have found it, the next step is to get Polaris positioned in the right part of the graticule.

If you ignore the fine mechanical polar alignment and go ahead to a 2 or 3 star alignment, the Synscan software (recent version) will report in degrees and minutes just how much the polar alignment is in error.

First, why are you using APT (I assume you mean the astrophotography managing suite) for (I assume) planetary imaging?

The exposure time for using an ASI462MC on planets should be milliseconds, so you definitely should not get any lag. 

I use an ASI462MC with Sharpcap. If you do likewise, you should not have any problems. 

13 minutes ago, RosalinaandLuma said:

Don't I need PIPP to correctly align for AS!3 to get to work ?

You can use PIPP to  centre the video frames, and also crop the frame size and reduce the file size, but it is not an essential step.   If you need to buy a Windows machine to handle your astro capture and/or processing, it need not cost much compared with the cost of an 8" SCT and camera,  if you choose one of the many used refurbished business machines available on Ebay.

I've always used Windows so that I don't have to worry about whether a given piece of software is going to run or not.

AS!3 needs to be used in conjunction with Registax 6.   A newer alternative which does everything is Astrosurface.