Cosmic Geoff

Here is an image of the M97 Owl Nebula.  Taken with 102mm f5 achro, ASI224MC camera, live stacked, 10 frames x 30 sec, processed in GIMP.  Bortle 6 skies.

I have the 127mm Celestron Mak SLT - a variant of some of the outfits you have been considering.  The 127 Mak is at the upper limit of what this mount will handle, and with the tripod supplied is only fit for visual use. The SLT mount does a bit better when custom fitted to a home-made wood tripod. Contrary to what some people claim, the capabilities of entry level mounts with a max capacity of 5Kg will be limiting.

I now use a EQ5 Synscan for some of my attempts at imaging. It is neither cheap nor particularly easy to use, but does deliver a good stable imaging platform.  The EQ5, like the AZ4-2, has a 1.75" stainless steel tube tripod - a good solid tripod and like scaffolding compared with all the lighter weight tripods that come with the entry level kits. Similar tripods can usually be bought separately.

I have used both the Celestron Nexstar software (in allt-az form) and the Skywatcher Synscan (in EQ form) and find the Nexstar much more user-friendly.

Here is an image of NGC3242, taken with my CPC800 and f6.3 focal reducer, processed in GIMP.  Camera is ASI224MC. The sky was hazy.

A lot of CMOS astro cameras are sensitive to infrared. Check out the specs of the ZWO ASI224MC, for instance. I have used mine to image planets in near infrared, with an IR-pass filter.

All DSLR cameras have an IR-cut filter, which some astro users are keen to remove...

Just for clarity, the optical tube assembly is a "C8".  The "8SE" or "C8 SE") is the whole outfit including the 6/8SE mount which is essentially a portable visual mount.

In answer to your question, the suitability of the C8 for imaging depends on what you hope to achieve.  I found that mine is good for planetary imaging, but (in the form of a CPC800) was not much good for imaging smal fuzzies until I got the Celestron f6.3 focal reducer, which has transformed it and it now takes nice images of planetary nebulae.

Since you already have the C8 OTA and th CGEMII, I suggest you buy the focal reducer (often available used) and give it a go. It will give larger scale images than the Stellamira 90mm.

13 minutes ago, Paul_Sussex said:

Also, regarding Malc-c's comment - "...and I dare say there will be those with long focal length refractors or MAKs that have used reducers and taken stunning images of DSO's..." - I'm guessing this can be used to produce a shorter focal length? Does this degrade the image at all? Not something I'd be looking at immediately, but this would seem to make the MAK a more flexible choice?

Yes, as the name implies, focal reducers reduce the effective focal length (just as a Barlow lens effectively increases it). I have not come across any focal reducers sold for use on Maksutovs.  They are frequently used with SCTs ( and I can personally attest that they make a huge difference if you want to image certain objects with a SCT). Focal reducers are also used with the varieties of refractor used for imaging.  The reducer will not degrade the image, and indeed may actually improve it if combined with some other function.

Note that focal reducers are not cheap. (Some of them cost more than your entire £500 budget).  The alternative, of course, is to buy a scope with a faster focal ratio in the first place. Such as (in the budget range) a f5 Newtonian, or one of the Skywatcher Startravel short-focus achromats.

Paul- if you are ping-ponging between various designs of 'scope and mount, I would suggest you take a systematic approach to narrow down the choices:

Portability - how far do you have to carry it?  Weight (you can look up the spec)

Assembly time - this can vary vastly, from carry it outside and start using it, to over half an hour with a complex setup.

Visual or imaging?  If you have a clear idea that's good. For visual, you can avoid equatorial mounts unless you particularly want a manual mount that rotates about one axis, or tracks with an electric motor.  An alt-azimuth GoTo will track on both axes.

GoTo or manual? GoTo can save you a lot of observing time, once setup, but some people prefer the old-fashioned approach.  

Manual or equatorial GoTo?  For visual the alt-az GoTo is much less bother to set up, and you can also image with it - you'd be surprised what is possible.  You only need an equatorial GoTo for the more challenging long-exposure imaging.

Dobsonian design - vey popular because of low cost and simplicity - but GoTo versions are no longer cheap, and none of the Dobs are well suited for any sort of imaging.

Focal ratio - be aware that different telescope designs have different focal ratios, which have a bearing on what they are best suited for. 

That said, it does not matter hugely what you get, so long as it is usable and of decent quality. Once you have had a go with it you will have some valuable experience and can buy something else if you feel the need.

Your money would be better spent on an EQ5 Synscan (used) or on upgrading a used manual EQ5.

The SCTs are lighter and more compact. And if the SCT and the Newtonian are mounted on GoTo mounts of equivalent performance, the argument that the Newtonian is cheaper loses much of its force.

I have owned both types, and there is no way I would want to revert to a Newtonian.

I have reently acquired a f6.3 focal reducer BTW.

It depends on the seeing.  I soon realised that I could get better views of the planets by imaging than visually.   And I realised after a while that even with an 8" SCT the results were variable, apparently dependent on the seeing.  I read that the most fanatic planetary imagers take their big SCTs to the Carribean, where the seeing is better than in the UK. 

 And if you want to "dabble in deep sky" a much smaller scope would do to start with.  Many deep sky imagers use small refractors rather than big Newtonians.

Many astro cameras eg. the ASI224MC require an IR-cut filter to achieve the correct colour balance with an OSC colour image.  I do not see that any other lind of filter will be any use for EAA of galaxies.

I bought a used EQ5, added a single axis drive and manual Dec slow motion via a knob or long rod, and later converted it to Synscan. I was not aware that there were two possible positions for a Dec motor - you can see where I put mine if you look at any pics of a Synscan EQ5 mount.

I think you can dispense with the manual slow motion knobs. My RA drive had a clutch that disengaged the motor but it was too fiddly to use and I never used it.  For fine adjustment you can use the electrics and for coarse movement disengage the mount clutches.

40 minutes ago, dazzystar said:

Can you explain why I need it please and how the length is calculated please?

Short answer: because you do... your scope was not specificically designed for attaching a ASI183MC camera - it was designed for use with a diagonal and an eyepiece.

If your experiments so far don't indicate what size of extender you need to get within the focuser's range, you could buy a set of T2 estenders, eg this one: https://www.svbony.com/svbony-extension-tube-M42/

I bought a set of Svbony extenders which may not have been this exact one.  One of these extenders or a combination of them should get you sorted.  I assume your camera has a T2 thread if you unscrew the nosepiece (if it has a nosepiece).

A picture of your intended setup would be useful.  I have a Startravel ST102 and find a planetary camera will come into focus with a diagonal or an extender.  To focus a DSLR, a T2 extender about 2" long  is needed.

27 minutes ago, StevieDvd said:

I read in later SW mount manuals where 11-15v is specified that the 11v needs a higher amp rating quote:

"Output Current: 4A for power supply with 11V output voltage, 2.5A for power supply with
16V output voltage."

So perhaps the psu you have does not have enough amperage to supply a steady 11V.

That is curious behavior, but quite possible for a switch-mode device which boosts the voltage up to a constant level. (There is an indication elsewhere that these mounts develop a higher voltage internally to drive the motors.) At one point in my career I was designing (not too successfully) a switch-mode power supply that boosted a battery voltage up to a constant level.  I found that the lower the input voltage, the greater the input current (as above) and that a nasty feedback loop was liable to develop which dragged the input down...

4 hours ago, WilliamAstro said:

I want to use my Skywatcher for imaging.

In that case you should start saving up for a mount and tripod suited for imaging.   As an absolute mimimum, I'd suggest an EQ5 Synscan with 1 3/4" steel tripod, unles you want to settle for a DSLR + telephoto lens + tracker mount.

  You can put other small telescopes on your SLT mount up to its weight limit, and even try some short exposure imaging.  What do you think the Star Adventurer Pro will do that the SLT won't?

EDIT: I did not know the Star Adventurer Pro was a star tracker...

10 hours ago, WilliamAstro said:

11 hours ago, WilliamAstro said:

Sky-Watcher Star Adventurer Tripod - Widescreen Centre

is this good for it?

Depends what you want to do with the mount. The weight and load capacity of the tripod (given in the link) clearly indicate it is intended for use as a portable visual mount, rather than for imaging.  For about £30 more you could buy a much more substantial Sky-watcher tripod with a flat top and IIRC a 3/8 screw.  The tripod in the link will be as wobbly as your SLT tripod.

I have done some EAA (EEVA) with an alt-azimuth mount.  I did not use a DSLR (and some DSLRs may prove entirely unsuitable for EEVA).  I use a ZWO ASI224MC for my EEVA (mainly because I already had one I bought for planetary imaging).  I use Sharpcap 4, which also supports plate-solving.

A check you could do is to put your 25mm Plossl kit eyepiece, that you probably got with the scope, in the focuser, focus it on a star, and then check that you can wind the focuser inwards by 5 to 6 mm.  If you can't, you may not be able to bring an ASI224MC to focus, and if you can't focus that, you may not be able to focus any other camera either.  

I don't think a recommendation as such is necessary - any machine that runs Windows and isn't ancient should be adequate.  Ebay is awash with ex-business laptops running Windows 10, refurbished and sold on by dealers, going for low prices.

And don't put all your childhood pictures on a laptop or any other machine unless you have a backup.

The #1 problem with slimline laptops is the hinges - they get stiff and rip the screws out of the slim plastic mouldings.

I use a Dell Vostro 5468 which is several years old.

Electrolytic capacitors do age and fail with swollen tops, so you should definitely replace the two capacitors as suggested above.

You say that the mount works OK with the handset, which indicates that the fault lies with the other stuff.

We used WiFi to connect laptops in a lab where I once worked, but had to take it out because the other gear in the lab interfered with the wifi, making it useless.

Don't assume that accessories that some people have fitted to their telescopes will be needed on yours.  I have had a CPC800 for several years, used it for visual, planetary imaging and some deep-sky imaging, and so far have not been troubled by mirror flop or felt the need to invest in a Crayford or an electronic focuser.

The most effective way to find focus is to focus visually on a small bright object e.g. Venus, Jupiter or a first magnitude star using  the stock 25mm Skywatcher eyepiece.  Pull the eyepiece out by 5 to 6mm and refocus. Now remove the eyepiece and fit the camera with its 1.25" nosepiece.  The camera will not be in focus but shoud be close enough so that you can now see a blur circle (or blur donut) on which you can focus if you have a roughly suitable gain and exposure time (try gain =300 and exposure time of 10 to 100ms). The in-focus exposure time for Jupiter is only 2 to 4 ms, as the camera is sensitive. 

Apologies for stating the obvious, but you should remove the fisheye lens from the camera, and if you want to attain the correct colour balance in your images, you should buy and fit the ZWO IR-cut filter to the nosepiece.

If your focuser has insufficient in-travel you may not be able to get focus for the camera without using a Barlow lens etc. I recall that when I had a 203mm Newtonian, the planetary camera I had only focused with the focuser at the inner limit of travel.

An EQ5 Synscan not behaving well? What else is new. 🙁

1 hour ago, wookie1965 said:

Sirius quite close Mirach just on the line of the inner circle of the Telrad OK all fine final star Arturus now this was nowhere near the Telrad circle nearly two full 5/6° circles away. 

I assume this is referring to the alignment routine. I'll refer to my experience with the mount, which I still have not totally mastered after nearly two years since upgranding it.

The initial movement from the home position often fails to accurately locate the first star, or the second.  As for a three star alignment, I have given up on that - it's hard enough to figure out where the alignment stars are with a two star alignment. Give me a Nexstar alignment procedure any night of the week.

I have found that if one does a good polar align followed by a two-star align, using two alignment stars on the same side of the meridian, the mount will then perform on that side of the meridian with gratifying accuracy.  However if you want to GoTo an object on the other half of the sky, then tough, you are back to using the finder or a Platesolve & resync, unless you want to go through the alignment process again with a fresh pair of stars.

I have found the mount works well in conjunction with an imaging scope and Platesolve & Resync.  If I was using it with a narrow field visual scope I would probably have concluded by now that it was a waste of space in my storage facilty.

I assume we are discussing the hardware Starsense camera and handset here, not the smartphone app? 

My suggestion is to get the system working without the wifi etc and then add the wifi and ipad.

On 04/03/2022 at 21:37, West Lancs Bri said:

The WiFi worked fine off the adapter to the app, longitude and latitude all fine, the scope aligned 3 stars and invited me to calibrate. I picked Sirius on the app, tapped the app and it slewed nicely in its general direction. Then using a 25mm lens I couldn’t see anything…all dark. I slewed slowly around the periphery of Sirius and still nothing. I sent the scope to Rigel and same result.

You might have to temporarily refit your finder (without unplugging or powering down the camera) if the alignment is a way off.

There is sure to be a pair of screw positions somewhere on the back rim to which you can fix the finder once you have bolted on your dovetail bar. Whether it will be in the ideal position is another matter.  There may not even be an ideal position, given the positions an equatorial mount gets into..

However if I were you, I would consider selling the complete CPC800 on and buying another OTA.  This would give you the option of buying another C8 OTA (possibly making some money) or going for an Edge HD or one of the new Classic Cassegrains.