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The focuser on my SkyWatcher 150i is a basic rack-and-pinion, unsurprising for the price point, but sometimes a bit of a pain to control finely enough. I’m not looking to spend any serious money upgrading it, but I did want to see what I could tweak.
The first thing I did was to slacken off (slightly) the screws holding the plate against the spindle, as the operation was very tight when new – that helped a bit (and I think that without doing this first, the “friction fit” approach described below wouldn’t have worked). I will eventually get around to taking it all off as per AstroBaby's tune-up.
Improving the fine control without a major change means doing something with the focusing knobs – they’re quite small, so the effective “gearing ratio” when you operate them is on the harsh side. Some folk have described fitting larger diameter replacements, either bought or made, and even using ones with a planetary-style mechanism to achieve a reduction in the ratio. I didn’t fancy this, as I couldn’t see how the existing knobs were attached to the spindle without trying to prise them apart (possibly terminally). The other option is to increase the effective diameter of the existing knobs, for which purpose a clothes peg is apparently quite popular, but I’ve also come across descriptions of chop sticks inserted into holes drilled at intervals into the circumference, and punctured lids from peanut butter jars.
I wanted something that was cheap, relatively tidy and non-destructive. The answer seemed to be some sort of thick sleeve that I could fit over the knob. It would need to be a tight fit so as not to slip in use, to be not so large as to foul against either the focuser tube or the main OTA, and to be thick enough that it didn’t flex sideways when grasped. I thought I might find some larger rubber washers that would do the job, but none were thick enough to be rigid in use. However, a bit of searching found these spacers that are apparently used in vehicle shock absorbers.
My calipers said the diameter of the focuser knobs was around 29.5mm, and the nearest spacers that were available had an internal hole 30mm and outside diameter 60mm. I ordered one that was 10mm thick, not quite as deep as the knobs, but which allowed a bit more space on the inside edge for free operation. I’d hoped the internal hole might be a but undersized when it arrived but it was spot on, so I wound five or six turns of masking tape around the knob first. To avoid taking the tape off when fitting the spacer, I positioned one side first and stretched it across the face as I pushed. When it’s flush with the knob’s outer face, it’s just clear of the focuser body and OTA. There might be enough room to stick some kind of friction surface around the outside to improve the grip, but I don’t think it’s going to be necessary.
I decided to do only the one knob, so I now have a very Noddy “dual speed” affair. Because the clearances around the fitted spacer are quite tight, it’s worth checking the positioning of the spindle in the focuser body first – mine was fractionally off centre, so there was more room one side than the other (assuming you have no preference).
I'm planning on getting a telescope for my son for Christmas (he'll be 6 by then). I want it to have some lasting potential and would rsther get a decent ish one so he can actually see things more clearly and retain his interest, although obv don't want to spend a fortune. However, we don't have a car, so in terms of opportunities to take advantage of dark skies, it would need to be portable. I was all set on the Skywatcher Heritage 150p and it seemed to tick so many boxes, and it kept getting tagged as very portable and great for travel, but I just noticed the weight is 7.5kg... so it may be portable compared to bigger ones, but I'm not sure about lugging it, a whole load of camping gear and two kids on a bus and a train!
Does anyone have any recommendations for anything similar spec-wise, where you can collimate both ends etc, that's also an easy set up and that's just a bit more lightweight?
Not posted some images since my introduction in the welcome section. With the dark nights finally back here in Scotland I thought Id share some of the DSOs I managed to capture back in Feb-April just before the light nights rolled in at the start of May.
These were all stacked and edited in PixInsight.
1. The Running Man and Orion Nebula - less than an hour of integration time (SA pro + fuji 55-200mm lens).
2. Bodes and Cigar Galaxy - Less than an hour of integration time ( SA pro + SW 72 ED telescope).
3. Flame, Horsehead, Running Man and Orion Nebula - Less than an hour of integration time (SA pro + fuji 55-200mm lens).
4. Pinwheel Galaxy - 35 mins integration time (SA pro + SW 72 ED telescope).
5 Whirlpool Galaxy - 21 mins integration time (SA pro + SW 72 ED telescope).
6. Andromeda Galaxy - 1.5 minutes integration time (Move Shoot Move + fuji 55-200mm lens).
I took a shot of M13 as a first test of my new orion 8 f/3.9. I have a couple of questions about the final result.
orion 8 f/3.9 mount skywatcher eq6r-pro canon 500d - astro-modded by me 40 exposures of 90 seconds and 40 darks 200 bias 200 flats capture software: nebulosity4 guide camera: zwo asi120mm guide scope: svbony 20 (80mm - 400mm) guide software: phd2 Processing:
siril preprocessing: align/callibrate/stack) siril post-processing: green nois reduction/ photometric noise reduction (very cool!)/deconvolution Result:
I attached a screenshot of siril (as the tif or jpg export did not show these "problems")
after preprocessing, I still have 2 problems (see the marked areas); what can be the cause of that? Are my flats not "correct"? The big mark, is a spot on the sensor, that is the "collateral damage" of me removing the Ir-cut filter. The other mark must be an other issue, I don't know so far the right part of the picture, shows some sort of glow; there was no moon during capturing; I live in a bortle class 5 area, but street lights are dimmed after midnight, till 05:00am and shots were taken around 01:00am. what can cause this glow Other remarks are very welcome - I hope to learn from it.
Thanks in advance,
I've been dabbling for about a year and am having a lot of fun.
Nothing too serious and I don't have mega expectations but I'm starting to wonder if my images could be sharper and there's something I'm missing.
I'm attaching a picture which is the best 10% of a 3 minute video with 500d 'bolted' straight to the 200p f5 scope. No filters...no barlows...just camera straight on.
It's sharpened and saturated after the fact so in every way this is the sharpest I can get it.
I've always had the same issue whether it's with a single shot, stacks of shots, or stacked video.
Views through the eyepieces (circle-T 12.5/25) are mega sharp!
I'm happy that collimation is very good and it was a remarkably clear night tonight.
All in all I'd be pretty happy with this image (maybe over exposed a bit...) if the craters with shadows didn't make me want to rub my eyes.
Thanks in advance for any thoughts or advice!