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I have an old Lunt LS60T telescope (tilt-tuned) and also two 5Omm Lunt aperture filters (tilt-tuned). These come from before 2010, the early days of Lunt.
The LS60T came with the B600 blocking filter and the 50mm filters with the B1200 filter.
I also was very concerned about the highly uneven illumination the Lunt 60mm gave both visually and in images, and did extensive tests, including pulling the filter units apart and using the blockers separately from the diagonals, in a straight-through configuration using an adaptor I made on my lathe (invalidating all warranties obviously).
My conclusions were:
1) The B1200 gave very much better results than the B600, with all other components being the same. It was chalk and cheese, the B600 just seemed to be a low-quality item.
2) The straight-through configuration was better than using a Lunt diagonal, and substituting a 2″ mirror diagonal from another manufacturer was better as well, though not as good as straight-through. When I pulled the Lunt diagonals apart I noticed how crudely and inaccurately made they were, components just glued with a rubbery substance to rough aluminium castings, the inside a total contrast to the polished outside finish!Since then I have taken all my images with the straight-through system I made incorporating the B1200 and a replacement IR block filter (the original Lunt IR block filters all crazed over after a few years; this is likely due to the dampness in my observatory). That said there is still an unevenness in my images from the Lunt that cannot be completely removed by any adjustment of components. Here’s a typical example. Not flat frames have been used.
Flat frames will (or should) correct Newton’s rings (which I get with certain cameras), but will not make the uneven filtration of Lunt systems even. In other words, even if you flattened the illumination, you would still see the uneven detail. The only H alpha telescopes I have experienced personally that do not suffer from such unevenness at all are the Solarscopes made in the Isle of Man (3 times the price of Lunt). However, I’ve been very impressed by images from users of the new Sky-Watcher Heliostar and Acuter scopes.
Attachments:
I believe so. BBC Sky at Night magazine did a comparative review of diagonals:
https://www.skyatnightmagazine.com/advice/what-is-diagonal-telescope-used-forThe grease dries out. I’ve had my Astro-Physics 900GTO for about 20 years and I did remove the gear covers and add the manufacturer’s recommended grease once about 5 years ago. I’ve never serviced my 15-year old Astro-Physics 1200GTO but it sounds grindy now, so it needs it. They are both in sheds. I doubt that it would matter much if you used a different grease. I am sure this frequency will depend on the make of mount and how well sealed it is. They are certainly not like bikes which do need servicing every 2 years, at least, if you ride regularly.
European institutions including British will need to step up to fill some of these gaps. We’ve relied on the Americans too much to provide important parts of our infrastructure, in science as in other areas.
The press (or at least the Guardian) has caught on to this. They are asking for readers’ images of 2025 F2: https://www.theguardian.com/science/2025/apr/10/share-your-pictures-of-the-comet-c2025-f2-swan
Time was when it was hard to get the national press to cover an eclipse, but now its bizarre which astronomical happenings (or non-events) they will run with: a mag. 9 comet hard to see from the UK in morning twilight. I suppose they can’t claim a ‘rare planetary alignment’ or ‘supermoon’ every day.
I don’t have an ASI cooled camera, but with the cooled cameras I have tried, it is possible to switch the cooling off in the control software. The disadvantage of cooling is that it can result in misting or frosting within the camera, especially if it is kept in an observatory at outside humidity. Combatting this can be a bit of a battle, though obviously there are strategies, e.g storing with desiccant, warming before use. I know of no other disadvantages of cooling. In theory a cooled camera should be more sensitive for all exposures, though for the short exposures used in planetary imaging, the benefit is negligible.
I think they will be very similar. The QE doesn’t seem that relevant as you will be imaging against a bright sky I suppose. Pixel size doesn’t seem important either when imaging such a nebulous thing. The larger well depth of the colour camera may give a slight advantage in pulling out a fine discrimination of brightness levels.
This sounds like a rather similar problem to the twilight imaging of the dark side of Venus, where the results are critically sensitive to altitude and sky darkness. Martin Lewis did a lot of work in quantifying the effect of noise in those observations. He gave a talk on it to a BAA meeting a few years back, which is in the YouTube archive.
Yes it is dirt somewhere in the optics near, but not on, the sensor. It seems to shift with the solar disk because it is casting a shadow on the sensor.
Yes it was a live feed at just before 18:30, and then another one just before 22:30. These could be a first. I had it all ready to go before 18:00, then a shower of rain came across and I had to cap the telescope, but I left the run-off roof open, as to close it I would have had to park the scope, and might not have been able to get Jupiter on the chip again in time. Fortunately the cloud moved off quickly, stuff hadn’t got too wet, and it all worked at the right time.
Yep, there’s no why that Saturn can be seen now without a telescope, low horizon and knowing precisely where to look, and obviously Neptune is totally invisible. I did a thing for the BBC news 6 & 10pm yesterday where they wanted a live image of a planet. Unfortunately they didn’t let me speak. If they had, I would have tried to inject some realism by explaining what people can really see.
Terry Pearce who runs the Amateur Telescope Makers of London club (see the Journal 2024 August edition) and the firm Vacuum Coatings (Scientific Mirrors) seems to be able to get these supplies. You can contact him via http://www.scientificmirrors.co.uk.
David
It is inconsistent and is a policy of the individual Section Directors. When I became Director of the Equipment & Techniques Section I determined that the Section Newsletter should be a service for members only. But some of the observing sections wish their publications to be open access and they take contributions from non-members. There are many, many inconsistencies in how the BAA is run!
Registax became unusably slow for me several years ago. It was not designed for images of the size that modern cameras (or even not particularly modern ones) produce. I second the recommendation of Astro Surface, which is free.
One thing I wish is that there were a viable stacking program on the Mac, as Firecapture and ZWO cameras work very well on the Mac. As it is, I transfer back to PC to use Autostakkert!.
Dear Jack,
I can probably be at Saturday Astrofest. I’ll definitely be at the BAA meeting on 18 January and can bring the mount head.
I agree the slow motion rods are not very good. I think I bought some longer flexible rods to see if they worked better, but I can’t recall if they proved effective.
David
With respect to James’s original questions, I think they were answered in this interesting discussion by Dr Mark Kidger from 2020:
https://www.youtube.com/watch?v=yYK-28E8c0AWhat struck me was his assertion that Betelgeuse will be a point of light that is as bright as the full Moon, and it will not be possible to safely look at it with the naked eye, let alone any other instrument, without heavy filtering.
I took one of these apart, but I’m not sure if I took it apart in the way you want. I was trying to improve the azimuth bearing (not really a bearing, just a screw), but it was not improvable. I discovered these mounts are mechanically of poor construction, and if yours has gone wrong it may not be worth trying to fix. I junked mine but used the legs, which are fine, as a tripod for a Sky-Watcher Star Adventurer mount. I still have the upper part, which you would be welcome to have if you want to try to use it as spare parts for yours.
Yes 4 pages of the Handbook are one sheet of A4.
I don’t know the exact maximum number of pages that can be stapled. The printer can tell us, but the other printer who quoted couldn’t do more than 100 pages, so we must be close to the limit now at 120 pages.
Thanks Nick for those tables of Uranus and Neptune data. I think exactly those would be useful to include. Central meridian longitude tables would probably occupy too many pages, and anyone involved enough in observation of these planets will know how to get these data from WinJUpos anyhow.
If it had too many more pages the Handbook could no longer be stapled as one unit of folded A4 and would have to have a glued or ‘perfect’ binding, which some would not like, as it could make it harder to keep open flat.
