dazzystar

I built Robert Brown's autofocuser...or a slightly modified version of it...was a tad complicated for me but.....

I don't have a heated dew strap yet but am sure I'll need one for me ST102 at some stage. I thought these just ran off 12v and were either on or off. Are the pots on the motor controllers varying the voltage to the heater?

If you find a circuit, let me know!

42 minutes ago, Clarkey said:

Circuit diagram!!??🤣 Sorry - I wouldn't have a clue! Here are some pictures - as I said no award for neatness. Basically all the bits are from ebay / amazon. Standard RCA sockets for the dew heaters, 12V usb sockets, 5A PWM circuit boards and 5.5mm x 2.1mm. They are all fed directly from a 12V DC cigarette plug via the quick connector boxes as it is a bit easier than soldering them all. The box is an external junction box. (I can send you the amazon links if you want)

I have not tried the 5A PWM yet - previously I used 10A units, so I don't know about reliability of these yet. The 10A have built in heat sinks which are missing from these. However, as I am rarely drawing more than 1 amp they should be OK.

There probably should be some more fusing built in other than the 10A fuse on the feed, but that is a personal think. Any short on the 12V outputs will instantly blow the main fuse and the PWM will blow above 5A (or a short) so I am willing to take the risk.

As I am running on a 13.8V regulated supply the voltage drop on the 0.75mm2 cable is not an issue. If running from a battery supply you probably want to use a 1.5mm core on the main supply cable so the voltage drop is not too much.

Hope this helps.

I'm sure there will be more expert electricians on a bit pointing out all the defects! But I have made a couple of these and not had any problems (yet).

 

Great!

Where and what model number are the PWM dew heater modules? I'd use a buck converter for the 5V USB lines on mine.

Hi All,

I want to mount my mini pc to either the top or bottom of my Startravel 102 scope. I've purchased a new 11" Skywatcher dovetail bar for this purpose. Originally, I wanted to mount it underneath the scope but my only reservation is that mounting it this way would mean I'd lose access to the front two cone error adjustment bolts.

What do you guys think?

Cheers
Daz

13 hours ago, Clarkey said:

I don't have plans but I have just built my owner 'powerbox'. Nothing too fancy, 4 12v outputs, 4 USB 5v outputs an two variable dew heater outputs, all from a 12v supply 10A total. In theory it could be customized to suit. Probably cost about £50. Yes, its slightly bigger and less elegant than a Pegasus, but I'm tight😄

Happy to share photos. (Sparkys look away)

Yes please. Love to have a look. If you have a circuit diagram too?

1 hour ago, Cozzy said:

Hiya Daz.

give this a read, there is a comment about 7 or 8 comments down that may help. He says the TS2FF works great in my Bresser AR-102

https://www.cloudynights.com/topic/666362-field-flatteners-for-achromats-visual-only/

 

hope that helps a bit.

Tim

Thanks. What's a Bresser AR-102 though?

Hi All,

Done the usual searches but can't seem to find a field flattener that says it's compatible with my Startravel 102 scope. Can anyone recommend something or point me in the right direction please?

Cheers
Daz

18 minutes ago, rl said:

There may be a couple of points to make here...you don't tell us what cameras you are using which may invalidate some of my comments. I'm not sure what experience you have but your question possibly implies you are just starting out with astrophotography. 

A guidescope only has to work....by which I mean that all you need is one star in the field with a good enough signal-to-noise ratio on which to guide. Once you're guiding properly there is not much point in fitting a bigger guide scope. There are a number of parameters to trade here; aperture  can be traded for exposure time to some extent (improving signal-to-noise) , which comes at the cost of update rate on the mount. If you're imaging in the milky way then a very small aperture (25mm) may well be enough. If you are pointing at the more barren parts of the sky then the bigger the better but 50mm aperture covers most situations with reasonably short exposure times (0.5 to 2 seconds).

As regards focal length, a longer focal length will allow better detection of guiding error for a given camera pixel size, at the cost of smaller field of view and hence choice of guide stars. Software like PHD2 can calculate the errors down to a small fraction of a pixel so the guidescope focal length can be a small fraction of the main scope.

To cut the waffle and get to practical options; Your main scope has a f/l of 500mm; I would expect either a 30mm aperture 120mm f/l or a 50mm 200mm f/l to give good results with normal guide cameras assuming the mount is aligned on the pole reasonably well. Half the secret is minimising the amount of work the guiding system has to do in the first place. Mechanical stability to eliminate flexure will be more important than the exact aperture. 

A word might be in order to manage expectations. Assuming you are starting out in astrophotography, a ST102 ain't the ideal scope for several reasons. The Chromatic Aberration will be severe and worse than seen by the  eye since a camera will be sensitive over a greater range of wavelengths. The field curvature will also be severe which will show up if you're using a DSLR. But if it's what you've got then have a go...we all have to start somewhere and it will still let you see stuff in greater detail then the naked eye will ever show, even with a few purple haloes. Just don't spend too much cash on kit that can't be used on a better setup in the future.

Thanks very much for the reply. The camera is an ASI183MC (not cooled).

Thanks.

Hi All,

Can someone offer some advice on the minimum size of guide scope to suit a Startravel 102 refractor (f4.9) please? It'll be used with a camera for guiding only.

Thanks
Daz

Hi All,

Looking to build my own powerbox. Does anyone know of any DIY plans that may be available? Something similar to the PPB.

Cheers

Daz

Hi All,

I have an EQ3 synscan (the tripod with the aluminium legs) and want to know what the max payload weight it can handle. The manual say 5.5kgs but want to know if anyone has any true to life weights. Also, I assume that max 5.5kgs does NOT include counterweights!

Cheers

Daz

thanks!

Just discovered another type of fixing...Synta....what is that now?

2 minutes ago, johninderby said:

The basic vixen dovetail that comes with your scope is strong enough to handle a fair bit of weight but would flex a bit with a heavy scope. However you can get much heavier duty Vixen type dovetails that will handle plenty of weight. The Losmandy is heavier duty still and being wider more stable but wouldn’t be thinking about one unless using a larger scope of say over 10kg.

Better Vixen type dovetail bar.

https://www.firstlightoptics.com/dovetails-saddles-clamps/stellamira-universal-vixen-style-dovetail-bar.html

Thanks. Only asking as I'm looking to mount a mini pc and the motor control box on top of the OTA using the two 1/4-inch camera holes on the existing scope rings and looking for a decent way to do it.

11 minutes ago, johninderby said:

Basicly the old narrow type Vixen style dovetail bars have been around for ages and are fine for lighter scopes. The bigger wider Losmandy type are ideal for bigger scopes but weigh more so not ideal for use on smaller telescope mounts whete the extra weight can be a problem. 

Dovetail saddles (the part that the dovetail bars fit into) come in three types. Vixen and Losmandy of course but also in a dual fit type that will hold either vixen or Losmandy but cost more.

Thanks for taking the time to reply. So, my EQ3 Pro saddle currently hold my Startravel 102 which is on a green Vixen style dovetail bar. Is there a weight limit or a guide to how much weight this can take before you should upgrade it to a Losmandy style one even if it'll fit my saddle?

Thank you!

Hi All,

Being pretty new to all of this, I'm getting confused by the terminology being used especially when it comes to mounting things to a scope. Does anyone know of a guide (or video) that explains all these terms so i can get to grips with it all? 

Cheers

Daz

On 18/01/2022 at 10:44, gilesco said:

I recommend perspex sheeting to attach to the tube rings of the OTA, easily orderable, much cheaper than a ADM plate, much lighter, pretty easy to drill holes in.

What dimensions is the perspex sheet you used?

Hi All,

I have a quick question for those more engineering minded than I. The focuser shaft on my Startravel 102 is chrome plated brass I believe and is not 'D' shaped like on the stepper motor so the two grub screws in my flexible coupler don't really have anything to 'bite' into. Does it matter or should I somehow file it?

Thanks in advance
Daz

I'll have a search on YT. Thanks.

Thanks. I'll have a look once I'm registered.

Do I need TF2 lithium grease or will lithium grease from Halfords be ok?

thanks!