ollypenrice

The Startravel fast refractors are entirely unsuitable for astrophotography. The numbers look good but they have massive chromatic and spherical aberration and their focusers are primitive and induce tilt. These issues are not so critical for visual use but the camera makes the most of each defect! Do not buy these for imaging. Olly

One common error is inputting the day as the month and the other way round. Worth checking that. The American format is month-day, the European day-month. Also check your tracking rate. You should be set to the sidereal rate. You can check your polar alignment easily enough without go to. This might be worth doing. Polar align, set the mount's tracking in motion at sidereal rate then move manually to centre a bright star, ideally close to the celestial equator in the south but certainly a long way from Polaris. Then just watch how quickly the star drifts out of view on a low power. It should take some time. If it drifts quickly then your polar alignment or tracking speed must be faulty. Olly

I've found v-section steel wheels to work best and I've also found that they work just as well running on dead cheap angle iron as they do on the far more expensive, dedicated vee rails. The angle iron is bolted to the support such that its flats are vertical and horizontal and the wheels run along the top edge of the vertical flat. This may even be better than the v-rail but it certainly isn't worse. We have used modified garage-door-openers driving bicycle chain twice here, on a large shed and a small. Both times it worked for a while but, in the end, both pegged out. We now use driveway gate openers, rack and pinion, and these are far more convincing both in their action and their longevity. If you choose this option I have one key tip: bolt the toothed rack not to wood but to a length angle iron fixed to the wooden roof. On two sheds we found that warpage in the roof timber threw the rack and pinion out of mesh fairly regularly with seasonal change. The angle iron comes between the warpage and the rack and keeps the rack straight. These systems are now very stable. Be sure to design in some anti-lift system to stop the roof flying off. They will if they can! Olly

Only a test will tell you. I do believe that. Theory is fine but it needs perfect data to be correct. The story doesn't end with the capture, either. What processing will the capture allow? That matters. Olly

Out of interest, why the Hyperstar? Why not the RASA, which is optically better? Olly

All of these number-based discussions must suppose that the system is diffraction limited. As the Hyperstar isn't, we cannot compare it easily with a system which is. Personally I've never bothered to look at the Hyperstar resolution theoretically because just looking at the pictures tells me I don't want one. There are, to be fair, tight NB images done through good filters with the larger aperture Hyperstars but I'm not a fan of broadband in this instrument. We can easily extract the maximum possible resolution for a 5 inch refractor from its Dawes limit. It's 0.97 arcsecs. What is not clear (to me at least) is whether or not this will support a pixel scale of 0.97". I wonder what Vlaiv thinks? We can be sure, though, that an instrument with a Dawes limit greater than its pixel scale cannot support that pixel scale. All I can really say is that I'm happy using my TEC 140 (Dawes limit 0.8") while sampling at O.9". I'm fairly convinced that the system is seeing-limited. Olly

My conclusion as well. Olly

Where do colour gradients come from? I have no idea but they come from somewhere. I live at a very dark site and still get them. When I used an OSC CCD camera I also got, quite routinely, a diagonal red-green imbalance, always in that chip orientation, similar to yours. I concluded that it came from the camera, not the sky, since it was always diagonal much as yours is. I don't say I'm certain about this, it was a long time ago, but it makes a strong memory. In any event, everyone gets colour gradients across images and you need to find a gradient removal tool you can live with. I use Pixinsight's Dynamic Background Extraction but there are others in AstroArt, Astro Pixel Processor and Gradient Xterminator. I wouldn't bust a gut over why gradients appear. They just do and you need to get rid of them. Olly

'Flats per filter' is a debatable point. Nineteen times out of twenty I use a luminance flat for every filter and have no problems whatever. If the R, G and B are not perfectly flattened individually, the combined RGB will be when it is illuminated by the luminance-flattened luminance channel. You just need to think through the process logically to see why this will usually be the case. When, exceptionally, it doesn't work it is because you have a truly remarkable contaminant on one filter. It happens, but very rarely. At least that has been my experience. Olly

The refocus distance is trivial in the scheme of things. You'll never tell the difference. I keep flats for as long as possible, which often means months. Olly

I have one sitting on my desk at the moment, frustratingly untried because we are still waiting for the new PC to run the rig. We ordered it from a French website but it ended up coming from Wakefield! I've seen superb results from this camera and look forward to getting it running. Olly

Just crop the one you like less before feeding them into ICE. Then it has to use the good one! I find it generally best not to give ICE a large overlap because it makes a mushy blend of the two at the overlap. Smaller overlap, less mush. Olly

That's a really crisp image, bold in colour and resolution. Just lose those bloody spikes to collect full marks! lly

The wheelbarrow handle/trolley solution is a good one and if it works in your location then you'll enjoy a 12 inch. Olly

I've only used sprays bought locally here in France, I'm afraid. There must be black stove touch up paints though. Olly

There is a difference between pigment-based paints and dye-based ones. Pigments are non-reflective in all wavelengths and are to be preferred for astronomy-blackening. Barbecue or stove paints are pigment based. If you have the tube upside down and only take a small amount onto your brush, doing so away from the tube, I can't see much risk. I don't recommend it but the effect of a drop of black paint on your mirror would be effectively zero. Olly

What is it? Olly Edit: ... apart from being the only TeleVue product I've ever seen which left my wallet fingers undisturbed!

OK, that's good. If you can't get the eyepiece in far enough to reach focus then the distance indicated is too long. The problem item is called a two inch to inch and a quarter adapter and this is a very odd one, the like of which I have never seen before. The narrower part of the body is very long and has an inexplicable bulge in it before the chromed lock screw. Like Fifeskies above, I suspect it may be in two parts. Does the bit to the right of the bulge (the bit underneath the world 'long' in my image) not separate from the rest? Fifeskies posted a picture of a conventional 2 inch to 1.25 adapter and you can see how much shorter it is Can we just check that the eyepiece is going in as indicated and that you are pushing it right down into the item on the right. I would contact your supplier and link them to this thread. Olly

I confess that this hadn't occurred to me. Vue is a feminine noun meaning view, which looks promising until you consider that the prefix télé in French requires two accents, both of which are strikingly absent from the brand name. So you haven't let Al Nagler off the hook, here, you've raised the charge against him to that of making deliberate spelling mistakes in two languages simultaneously! Heinous! (But quite impressive...) Olly

This looks very odd. Firstly that's not a star diagonal, it's an erecting prism. Note the 45 degree angle. And then I can't work out which bits are which. Could we have a photo of all the components separated and placed on a table? I don't think the rear assembly is correct at all. For one thing, how do you put an eyepiece in that? It looks as if the eyepiece end of the prism might be attached to the scope. Just pull it all apart and take a photo first. Olly

Any astronomical telescope is always, and in itself, a mass of compromises. If you add to those the desire to combine spotting scope with astronomical, the compromises multiply and become intractable. The aperture advantage of 115mm over 85mm is very significant for astronomy but not for terrestrial. An Amici prism will hardly degrade terrestrial images at all but will considerably degrade astronomical ones because stars are notoriously difficult targets for optics to control and because, in astronomy, edge contrasts are so extreme. The large size of an astronomical scope is a pest for terrestrial observing but a bonus for astronomical. I've tried using a smaller astro refractor for terrestrial but have given it up in favour of a budget spotter. As others have said, good doublet astro refractors may well beat average quality triplets in visual use. In astrophotography the colour correction into the shortest wavelengths picked up by the camera can require the triplet design but the human eye does not see as far into the violet end. With a doublet your budget goes onto fewer but better lenses. Olly

As a former English teacher I have an in-bred hostility towards names making deliberate spelling mistakes. This does not mean that my 13mm Ethos will ever be for sale. lly

Yes, that's par for the course and the time spent. There is a lot you could do to get more out of it in processing but that's a big subject in itself. Olly

In Ps you would simply process one image while saving everything you did as an action. Google Photoshop record action for how to do it. Olly

Bravo. Perfect. Olly