HEQ5 Polarscope dimmer

[Astro_Baby]

Well everyone bitches about the HEQ5 and its over bright polarscope illumination.

I have been contemplating doing something about it for ages but wanted something neat, compact, something that looks good.

A few weeks ago, as part of a different project, I found just the right control pot for the polarscope. Its a novel cermet pot where most of the gubbins are in the actual knob itself rather than behind the panel. What this means is the pot can fit to a surface where there is minimal clearance behind.

Voila - behold - an HEQ5 polarscope dimming pot. THis one is a 100k ohm which is what I calculated would be needed. It works but it doesnt dim the polarscope LED quite enough - I am going to try a 200k ohm next.

The 100k one does take some of the nasty edge off though and I am going to withold any more changes until I can test it out under a sky.

It was a complete perisher of a project by the way - theres so little space to work with but the finished result, I'm sure you will agree, looks pretty good. In fact in the flesh you would be hard put to know this wasnt fitted at the factory.

[Breakintheclouds]

Wow - that's an incredibly neat job. Excellent stuff.

[Jaffa007]

Great job!!

Where did you get the dimmer pot from?? :-)

[Astro_Baby]

The pot came from RS Components. They arent cheap at a £5 a bash but RS service is legendary in the electronics game.

If you do a search on their site for variable resistors and specify 'cermet' you'll find it. I will be testing this with a higher value pot - I think 200k ohm is whats needed and I'll let you know.

It is a complete swine of a job through. My estimate was about 40 minutes. In reality it was 4.5 hours.

To do it you need to get the DEC motor out of the way and take all the covers off the HEQ5. Drilling into the block that holds the connectors and power switch is the hairiest bit by far. Getting the nut on the back of the pot took about 20 minutes because theres next to no space behind.

When I test the 200k ohm pot I'll do a photo set of the various stages of how to do it.

[Jaffa007]

Thanks Astro, look forward to reading and seeing your write-up :-)

[brianb]

If you can get at the bulb (LED) you can also apply a dab of paint - I found a spot of SnoPake tamed the aggressive illumination in my Astrotrac polar scope. My HEQ5 Pro has been left alone, don't know why but I don't find the polar scope illumination excessive.

[Astro_Baby]

OH you have to get at the bulb to do this mod brian. You need to remove the polarscope illuminator to do the job right. Its very finicky and the initial wires supplied between the led and the motor board are quite short.

Heres a pic of the led and its fitting ring being removed.

I have thought about the red paint idea but its not appealing to me - I like the idea of an extra bit of stuff to fiddle with

[keithatrochdale]

You could always put a 100k resistor in series with the pot and thus lower the operating range of the LED.

Could also change the LED for another colour.

[Astro_Baby]

I did mess about a lot with this - trying various options out including a full on dimmer circuit which I ended up junking cos it was too big and inelegant

I thought about sticking in a 100k resistor in line but kind of rejected it because its just as easy to put another pot in and also neater.

There seems, from reading around, some evidence that Synta never make two mounts the same Apparently some HEQ5s have lower power LEDs or resistors added to dim them down a bit.

I found on ideal nights the polar illuminator is ok and in fact is bright enough to screen out any star of lower mag than Polaris in the area - ergo if your point North and at around 51' the ONLY star you'll see will be Polaris. The problem is on nights were seeing isn't so great the illuminator in my HEQ5 is so bright you cant see a thing hence the modification.

There were some posts on another board which suggest some versions of the mount have a 139k resisitor in series with the result the LED is so dim its useless as an illuminator. I suspect coming from a manufacturing background someone at the Synta plant ordered, and had fitted, some lower power LEDS while someone else tried to fix the problem by adding a resisitor end result too dim to be useful. That sort of stuff happens in a plant.

Anyway thanks to me forgetting to order the replacement pot you'll all have to wait a bit longer to see if 220k ohms is a maidens dream where this is concerned.

Like all Mels projects this one has had some cost and time overruns LOL - guess which computer manufacturer I used to work for

[Astro_Baby]

Okies - for anyone following this thread who wants to know what value pot to put in. I now have a 470k ohm pot in and its PERFECT - maybe a little coarse in the control but gives a good range of very dim to blindingly bright

Its the same pot as shown in the pic just a higher value. Over Chritsmas I'll probably write a complete how-to on this one.

[great_bear]

To do it you need to get the DEC motor out of the way and take all the covers off the HEQ5. Drilling into the block that holds the connectors and power switch is the hairiest bit by far. Getting the nut on the back of the pot took about 20 minutes because theres next to no space behind.

You really don't let anything get in your way once you've made your mind up, do you?

My HEQ5 Pro is about 4 weeks old now.

It seems to be just about right.

Maybe they've finally sorted it out...

[Astro_Baby]

You really don't let anything get in your way once you've made your mind up, do you?

Nope but it takes me ages to get projects going. I like to ponder all of the possible issues. I still have my rotating tube ring project to get round to - thats a bit of a biggie but its also elegant AND simple.

[oceanheadted]

Nice Mod Mel. Looks just perfect.

[Astro_Baby]

Well I said I would get round to writing up the guide to do this mod at Christmas - I know its a bit later but hey ho -

Anyway the guide is now at Polarscope Illumination Dimmer for the HEQ5/Sirius EQ-G

For anyone who may want to be brave - its a really scary mod I found

[jobe]

I still have my rotating tube ring project to get round to - thats a bit of a biggie but its also elegant AND simple.

i shall wait for this one with baited breath. if you want some tube rings as a project i may 'lend' you mine:D

[Astro_Baby]

Ahh the ring project is already done - take a look here Rotating Rings for Reflector Telescopes

I did post on SGL about it a few weeks ago (I think).

[Jaffa007]

Great guide

[TopHouse]

The only thing now is you've created a world shortage of 200mm rings as everyone's looking for some! methinks there's going to be a number of posts looking for 'ring buddies' to split pairs!

[philj]

What a nifty idea Mel, excellent. I wonder if they do them in lavatory wall white? I have the white HEQ5 Pro

[Astro_Baby]

Sadly not Phil BUT the black pot would look ok - most of the connectors are black on the mount and it has those black coloured plugs on one side. YOu could always paint the knob on it white I guess with some Humbrol Enamel - on such a small object a satin coat wouldnt show any brush marks.

[steve_bham]

Very neat job Mel, love reading your DIY scope mods.

[Herbig]

Hi, I'm a newbie to Astronomy and have just bought a C8 and HEQ5 Pro from FLO and was having the same problems with the Plarscope LED brightness. Did a bit of research on the net as I didn't like the idea of ripping the thing apart as I'd only just got it. Turns out if you have got SynScan that it is adjustable via the handset!

You probably need to up grade the latest firmware (3.27) - mine came with this version. It's then just a matter of going into the Set up Mode from the Main Menu then select Handset Settings and you should find 'Polarscope LED' as an option. Mine was set at 100% and I've now reduced it to 20% have yet to try it but it certainly has reduced the intensity. It's a shame the instruction book has not been changed as it seems this has been a bit of a problem for a while.

[Psychobilly]

Its also dependent on the Motor Controller PCB revision...

[Astro_Baby]

Yes, the dimmer off the handset only works on mounts with a version 2 Motor Control Board.