ollypenrice

40 minutes ago, seven_legs said:

The rak and pinion focuser seems a bit cheap.  But I've never had a Tel Vue scope so I may be wrong.

Heretic!  TeleVue rack and pinions are excellent; smooth, light and capable of holding heavy eyepieces without slipping. (This is a visual focuser, single speed.) I still have one on a 30 year old Pronto and the one on my merely 10 year old Gensis was perfect as well.

Everything about the build quality of TeleVues is designed to see the scope outlive its owners. They are fully repairable and adjustable as well.

I'm sure Magnus is right in that this is the F8.6. It certainly isn't one of the F5 scopes which are remarkably short, physically. (Edit: I took my F5 'Pearl River' Genesis onto a plane as carry-on.)

Olly

8 hours ago, Celerondon said:

It took me a moment but I think that that the center left view is the mounting flange for the dual (Type V & D) dovetail.  I have not pulled my mount out to confirm this theory but it seems to make sense.  Counting clockwise from the top left diagram they appear to show an AM5 that is in AltAz mode and aimed at the zenith from the:

1. south
2. west
3. below
4. east
5. above
6. dovetail flange

The north view which would have shown the back side of the wedge and the counterweight plug/toe saver is not shown. 

Don

 

I think that ZWO provides the flange diagram to show that it is easily possible to rotate the dovetail mount 90°. (This rotation enables side by side telescope mounting)  Compare the 38mm bolt spacings in position 1 and position 6 to see how this works. 

Many thanks, Don.

Olly

On 10/04/2024 at 09:41, Zakalwe said:

Thank you.

I wouldn't really describe it as fighting against challenging kit, more it's just a necessary step in the overall process. Achieving sharp focus and trying to beat the seeing (I use a 120mm Espit refractor with the Quark) are much, much more difficult than spending 2 minutes taking some flats.

Never having taken solar flats I just watched a good video on how to do it. The extreme defocus method was the one I didn't understand. How can this correct vignetting if the chip is sampling a smaller or larger diameter light cone?

The case for using flats is certainly overwhelming, as it is for DS imaging.

Olly

A very nice, natural-looking processing job. 

Olly

13 hours ago, Clarkey said:

I think I must be the only person on SGL that likes RC scopes. I'll be burnt as a heretic next! 🤣

I think you're safe. It's been so wet... 

Olly

What about relocating your gear to a remote hosting facility? I realize that this would leave your home observatory out of a job but not the rest of your kit.

(For transparency, I do some hosting but have no availability. Places in Spain are available, though.)

Olly

Don't look at a stretched version of your flat to decide. It tells you very little.  What you should do is read off the ADU value of the unstretched flat (ie the linear flat) in the corners and in the middle. I've found that it was perfectly possible to ask flats to correct a 25% drop-off in brightness between centre and corners, so you need to know what your light drop-off is. It may well be that your drop-off is greater than that but, before spending, it would be worth a check.

Is there any way in which you might get your filterwheel closer to the chip? You don't have any spacers between F/W and camera?

Olly

1 hour ago, 900SL said:

Very nice image of M51!  I think the focal length of an 8" SC would be too much for my seeing and guiding however, even with a reducer to 1400mm. Plus they are pretty expensive here, once I add in a reducer and OAG/focuser.  Thanks for the feedback though.

None of this makes any difference if you adjust your true and final image scale at capture and then processing to what the seeing and guiding can realize. If I went for a flatfield SCT I wouldn't use the reducer, I'd capture in superpixel and/or resample before processing. This would mean I'd get the extra light per pixel onto the target and not onto background sky which I'd later crop out.

Olly

1 hour ago, Fegato said:

thanks Olly, that's very kind - it was certainly one that took a lot of time and a certain amount of care! As for the Ha - well, I largely got the idea from this image, which has tons of integration and has found a bit more than I did, but to my mind is perhaps just a bit over-done in the processing / stretching

https://www.aapod2.com/blog/m45-pleiades-in-hoorgb

The image in the link is mighty impressive.

There are reds very close to, and within, the cluster which I think are ERE, Extended Red Emission, rather than Ha. UV illumination of dust produces luminescence in the 500nm to 1000nm range so it will pass through an Ha filter at around 656nm, though I guess in very small quantities. A broadband red filter will pass it far better. However, the reds on the left hand side of your image, between the pincer-like extensions from the cluster, look like Ha pure and simple.

Olly

An absolute cracker of an image! The blend was certainly the right way to go - which I would say because I do that all the time. 

Hat's off for the Ha. The received wisdom is that there isn't any and the received wisdom is clearly wrong. You have the deep satisfaction of having brought something new to a familiar target.

As for the rest, stars, background, dust, nebulosity - flawless. Take a bow!

Olly

First off, it's a very clean and workmanlike image of M51. Background and stars are excellent and spiral detail is well resolved. It's very good, surely.

The faint extensions are there and would show with more data. 5.5 hours has done a good job on the brighter stuff and has caught the blues in the extended tip of the 'bridge of light.'

To my eye the colour balance is a tad high in green and more significantly short on red at the brighter end, though the background looks good. I'm not suggesting it's miles out, it's just where I'd be looking if the image were mine.

SCTs tend to be very tolerant on reducer-to-chip distance but the true FL does vary considerably. Your variation from the nominal 1260mm is not remarkable and your intention to experiment has to be the right way, I think. While you are tinkering with this, bear in mind that all the arguments favour an OAG with this scope so it might be easier to fit one before agonizing over spacers.

Regarding vignetting, I think it's to be expected on this setup. The thing is to measure it. This is easily done on flats. If you measure the centre brightness in ADU you can compare it with the corners. I found that I could live with a 25% fall-off with my Tak 106 rig so, if your uncropped corners were at 75% of centre brightness you should be OK. If your corners were darker than that you could sample the flat on a line from corner to centre and find the point at which it reached 75%. That would indicate your largest workable field. (The reality of galaxy imaging is that you rarely need a large field anyway, at least in my experience.)

If I were you I'd be delighted with this as an opening result.

Olly

The roof behind the bushes is pretty sharp. So, interestingly, are the fence and some other items in front of  the bushes. The obvious conclusion would be that the unsupported branches of the bushes were moving in the breeze...

Olly

I'm sure you wanted your list to get shorter rather than longer but there is a conspicuous absentee in the form of the MN190. https://www.firstlightoptics.com/maksutov-newtonian/skywatcher-explorer-190mn-ds-pro-mak-newt-astrograph.html

This has both the right FL and an excellent aperture for high res imaging using a modern CMOS camera with small pixels. The faff factor is hard to predict and I've never owned one of these, but I think it would be less than with the RC. (I'll restore the list to its original length by saying that efforts to help one of my customers with an 8 inch RC flagged up a 'Never Again' alert in my mind. We gave up on it.) The MN190 weighs 10kg so I don't know if you could stay within payload with that but I think you might.

Why all this talk of reducers? Just make your effective pixels bigger by stacking in superpixel mode and/or resampling downwards before processing. Reducers are best seen as field of view wideners and my experience of imaging at high resolution (about 1"PP, say) is that I ended up cropping almost every image I shot in order to present it at full resolution without the need for click-to-zoom. The last thing I wanted was a wider FOV. (Ironically, the shorter the focal length, the more often I do mosaics with it.)

Refractors are certainly the easiest in what is a tricky business at the best of time. I have lots of nice results (I think) from my TEC140 F7 at 0.9"PP but I would shoot about 20 hours per galaxy.  The MN190's extra 50mm of aperture would almost halve that exposure time. If you factor in what you will really capture, aperture may outweigh pixel peeping perfection...

A big refractor 'plus' used to be the high quality stellar images but, with modern processing, you can get decent stars out of other systems as well.

Olly

8 hours ago, alacant said:

If it's any consolation, here we have dense calima; Saharan sand and dust. It's like having sunset and impenetrable haze. All day🤥

Coming our way, too. We had a good dump of it last week, though not as bad as in your image.

8 hours ago, gorann said:

I just saw this image of The Eyes on Astrobin. So there are some interesting details but you need a lot of time and a bit more focal length:

https://www.astrobin.com/v1x34t/?q=The Eyes of March - NGC 4435 and 4438

 

OK, I think that one's nailed it! 

Olly

6 hours ago, StevieDvd said:

The mount on its own has a flat base with many pre-drilled/tapped holes. The central being a 3/8" standard, but several others for the accessory plates (4 x M6 and 4 x M8).   Using the 3/8" alone would not stop  the possibility of the mount turning on the base, but would be simpler to make the steel plate. Dimensions are on the FLO page linked to earlier be @Elp

Thanks, I think that answers my question. The payload will be very small - a Samyang 135/cooled CMOS camera - so it looks like bolting the AM5 down onto a flat plate should be easy.

Olly

2 hours ago, Elp said:

Haven't got one (yet) but the drawing is here and on their website. I believe it comes with a silver puck which fits into their TC40 CF tripod and is removable leaving the flat base you see in the mechanical drawing showing the PCD of the fixing holes. One of the appeals of it for me is the standard 3/8 female for tripod mounting but you're looking for a more secure fitting which you can see from the drawing:

https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/zwo-am5-harmonic-drive-equatorial-mount.html

1 hour ago, StevieDvd said:

I have the AM5 and both of the extensions (PE160 & PE200). 

The AM5 on it' s own can use a 3/8" tripod/base but needs access from below.  The extenders  have the same top fitting as the tripod so you can 'drop' the AM5 into it and tighten the upper clamps.  You could bolt one of these onto the pier (permanently if needed).   I have one on my pier using the eq5 adapter (supplied) that can be bolted to the extension - but that needs access from below as well.

Thanks.  Sorry, but what I still can't work out is how to attach this mount to a home made pier. If my pier top consisted of a flat steel plate with access from beneath, could the mount be placed securely on that and bolted down onto it by bolts from beneath? Is the bottom of the mount drilled and threaded to receive bolts from below? Drilling the mount top plate is no problem since I do have a large pillar drill.

Olly

Hi all, does anyone know what would be needed to fit the AM5 mount to the top of a generic concrete pier like a Todmorden? I can't see what's going on under the bottom of the mount or the standard pier adapters.

If I put a flat steel plate on top of the pier, can the ZWO AM5 attach to that? And, if so, would it need access from beneath?

Cheers,

Olly

These old ellipticals don't have much by way of interesting structure and, since we're looking out of the plane of the Milky Way, there's nothing much in our own galaxy to provide foreground interest. 'The Eyes' galaxies probably provide the most rewarding detail, with their tidal interactions.

Paul Kummer and I have it in an 8 inch RASA, so comparable with the Hyperstar.  It's a wider field mosaic so it's on the enormous side as an image but here it is. You can do the clicks for the full res if you have the patience. I think the interest in this region lies in cruising the field in search of little surprises like irregulars and little spirals. It will never be attention-grabbing eye candy, so to speak.

https://ollypenrice.smugmug.com/Other/Galaxies/i-kTDJC88/A

Olly

On 05/04/2024 at 14:00, Stu said:

It’s funny, every day when I look at my handsome visage in the mirror, I don’t think it looks false 🤪

I’d rather see maximum detail personally but if slightly less but the right way round suits you, that’s fine of course.

A famous portrait painter once had a very dissatisfied customer who strongly insisted that the likeness was false. She had a more than averagely asymmetrical face and the artist realized that she was used to a mirrored view of herself, so he altered the painting to a mirrored view and she was satisfied.

I'd much rather not have the moon mirrored but put up with it because the rather basic erecting prisms I've tried really clobbered the image resolution. I've never tried a good one.

Olly

9 hours ago, Gerr said:

Wow, that must of been a privilege. My head on astrophysics is not that great but if I can get a pretty picture of it’s visible characteristics than that is enough for me.

😀Geraint.

Nothing wrong with that. René was here, he said, to see it and photograph it, perhaps for the last time. He was in his eighties and had too much LP to see it from his home on the other side of the country.

Olly

Lovely shot.

I had the pleasure of being host here, for a week, to Dr René Dumont whose doctoral thesis was on the zodiacal light and whose article on the subject is the very last in Moran's Astronomy and Astrophysics Encyclopedia. It was a delight to be enlightened on the subject by a professional astronomer and world authority, especially since he was such a truly nice man. (He and his wife were particularly attached to our affectionate dog and asked after her on subsequent Christmas cards. ) 

Olly

1 hour ago, Flame Nebula said:

Can you imagine the neighbours seeing you with your head stuck down the end of your Dob? 🤣

Although you might be left with a cross on your head from the spider. 

I hadn't thought of actually venturing down the tube to do this. An input fan on one side and an output on the other would be more comfortable...

lly

38 minutes ago, Piero said:

In my truss dobsons I pull up the light shroud about 3" from the mirror box. I find this to eliminate the formation of air boundary layer above the primary mirror as this cools down to ambient temperature. I also leave the fan behind the back of the primary mirror on, but at reduced speed.

It's quite interesting to notice how much "poor seeing" is actually very local.

Have you tried blowing air across the surface of the mirror? There's an argument which says that this is the best way to break the boundary layer.

I've never tried it and no longer have a Newt.

Olly

Just now, alexbb said:

Thanks! I knew you captured a part of the Monogem ring and I also saw some arcs near the Rosette nebula. Perhaps there are simply no images of the full ring in the visual spectrum and they are waiting to be captured.

I'll try to get in touch with Marcel and see if he knows and can share some more info.

This area is a 4 panel composition with a Sigma 135 F/1.8, ToupTek 2600 mono and an Astronomik MaxFr 6nm O[III] filter. 1h exposure / panel. Skies would be SQM ~21.2 in that area, captured at no lower than 30 degrees.

 

Skies and time allowing, I'll add to it. Though I also want to cover the missing panels already covered in Ha and RGB this season.

That's great, packed with things rarely seen.

Paul Kummer and I had fun in this region in broadband. 

Olly

11 minutes ago, simmo39 said:

Thanks Olly, depending on what pooter Im using at the time I do get a little variation in colour. One seems to give me more green and although on the one Im using at the moment the colour looks ok to me Im sure if I look at it on my main pooter it will look brown as you say. Ill have a play later and see if I can sort it.

For an objective measurement I checked the background brightness per channel in two places using the Ps Colour Sampler Tool (eyedropper menu.) I check these values regularly when processing.

It gave R40  G30  B19 and R38  G29  B19. A neutral sky would have parity in all channels though personal prefences also apply. However, the numbers do say 'red high and blue low.'

Olly