Xilman

On 2024-02-16 I read that the moon was lying close to the Pleiades. I already know that bright stars are easily visible through a telescope as long as they are bright enough and their position known.

Although my scope doesn't have absolute positioning the moon was easily visible through the finder and MaximDL would tell me its position at that time of day --- 13:30 local solar time. A 50ms exposure through a Sloan i' filter (to darken the sky background) showed nice craters. Syncing the mount to the lunar position told the telescope where it was pointing to around 10' or so.

Slewing to Alcyone showed nothing, which was not too surprising given that the field of view is only about 13'. Lots of slewing around at random produced some images containing stars. All contained a bright sky and lots of dust donuts. The starless images were stacked to produce a master flat.

Identifying the stars was not easy. Luckily one contained a double star. I know the image scale (0.6"/px) and the camera orientation (-177o) and so could estimate the separation at 9.6" and the PA at about 225o. I also knew the approximate image centre, to within 10' or so.

Lots of rummaging around in the DSS2 images, SIMBAD and the Washington Double Star catalogturned up HD23964 where the AB components are too close to be resolved with the seeing and the relatively poor focusing, but the AC pair has a seperation of 10.4" in PA 235o. Their I magnitudes are 6.74 and about 9.3 (estimated from R=9.71 and J=8.93). A very satisfactory match!

Another star in another image was somewhat brighter than the pair. 26 Tau, at V=6.46 and J=5.68, lay well within an arc minute of the predicted position. I am reasonably confident of this identification.

Here is HD23964AC

and here is 26 Tauri

You can see how well the impromptu flats have worked.

Given how easy it is to pick up 9th magnitude objects in the near infra-red with an exposure where the sky almost but not quite saturates the CCD, I think I’ll try to find some more Messier objects in daylight. Call me crazy if you wish.

Just now, vlaiv said:

Well, people do have good opinions on telescopes like Maksutov Newtonian and Schmidt Newtonian. Granted, those are full aperture correctors and not sub aperture correctors, but can be quite fast systems as well- often F/4-F/5.

Good point.  I was thinking of post-primary correctors rather than pre-primaries such as Schmidt and Maksutov correctors.

Note what I said about a meniscus lens. It describes  the important characteristic of a Maksutov corrector. Wikipedia has a good article on this topic, including the existence of sub-aperture correctors.

4 minutes ago, vlaiv said:

For newtonian with single curved mirror - it is true that spherical aberration increases rapidly with faster optics.

https://www.telescope-optics.net/reflecting.htm

For paraboloid - it's equal to 0 but for spherical with K=0, we can see that it is inverse of third power of F/ratio, so telescope has to be really slow, or have small diameter.

I don't doubt it. That's why I mentioned corrective elements. A Newtonian can be, but rarely is, corrected for SA with lenses in the same way as its coma (absent in a spherical mirror) can be and usually is in fast systems.  On the same site as my Dilworth is a 0.5m f/3.5 Newtonian astrograph which absolutely requires a coma correcting refractive element.

On 24/04/2024 at 17:50, vlaiv said:

If it's a longer tube - greater chance that it's spherical mirror. Fast telescopes and spherical mirrors don't get along. If it's F/8 or slower - then it might be spherical.

 

Not without corrective elements, they don't.  My  0.4m Dilworth contains nothing but spherical surfaces. A train of spherical lenses corrects for spherical aberration. Not sure of the focal ratio of the primary but guessing from the length of the OTA it is probably around f/2.5.  Take a look at http://www.astropalma.com/equipment.html to see what I mean.

For moderate focal ratios a simple meniscus lens will give most of the correction needed.

For photometry it may not matter anyway, as stars are generally defocused to spread the light over a larger number of pixels, thereby reducing the effect of pixel-to-pixel variations in sensitivity. My Beacon Hill 18" Dobsonian worked just fine as a light bucket for my (visual) variable star work, despite having very noticeable spherical aberration.

Horses for courses.

Here is my Nerd Test v2.0 Test result.

3 hours ago, Mr Spock said:

I want to know who the 1% is so I can eliminate them 

Same here. I also scored 99%.

0% scored higher (more nerdy),
1% scored the same, and
99% scored lower (less nerdy).

If one star is a white dwarf, it could be moving towards, away from, or be stationary relative to the Earth.

A strong gravitational field also creates a red shift which may be larger than the Doppler-induced one.

Curious. I very rarely find that an exposure of less than several seconds is usable with a light panel. The time required depends on the filter used, of course. Perhaps your panel is intrinsically brighter than mine.

FWIW, I would suggest you continue with your current practice. Do you have any evidence that the flats you take are unsatisfactory? That is, do you see any residual gradients, vignetting, etc after applying your flats to your lights?  If not, leave well alone - i.e. if it aint broke, don't fix it.

Some time ago I picked up a Celestron NexImage 5 which is basically a colour 5MP webcam. At the time there was no INDI driver and so after a bit of playing around with the Windows software the camera was stowed away until later.

Today I discovered that an INDI driver is available so fired it up under Kstars/EKOS and took some images, with mixed results. First, the image size is reduced to about 4MP. Second, only 8-bit images are recorded, despite the camera having a 12-bit ADC. Third, it appears that only the green channel is recorded when in RGB mode with FITS output, even though the FITS file contains three image HDUs.

Is this the best I can expect, or are there some configuration settings I have not yet discovered?

My thanks in advance to anyone who can help with this issue.

Paul

On 12/04/2024 at 13:54, TiffsAndAstro said:

Ty for this been trying to find it to download and struggled:)

I had problems too. If anyone else here would like assistance, please ask. Either by posting or by messaging me directly.

In particular, there is an excellent chance I still have the distribution kits stored on my systems.

One of these.  I already have somewhere to put it.

https://www.planewave.eu/en/products/telescope-systems/rc700-ritchey-chretien-f/12

I'd need to sell the house for it to become within budget.

The 1m version would be nicer but I doubt I could afford it.

Sundry 64-bit PC compatibles, both laptops and desktops.

SWarp, astrometry.net, APT, The GIMP, Siril, ds9, ImageMagick and even xpaint for annotation.

Oh [auto-Bowdlerized word which sounds similar to begger]! I forgot to mention sundry finders and guide scopes, all refractors with apertures in the range 0.05 - 0.12m.

At least twenty telescopes.

Thanks!

As dear old Oscar might have said: I have nothing to declare but my pedantry.

And my incompetence.

I have nothing to declare but my pedantry and my incompetence.

And a fanatical devotion to astronomy.

Amongst the thing sI have nothing to declare are pedantry, incompetence and a fanatical devotion to astronomy. And ...

I'll come in again.

I didn't expect the Spanish Inquisition.

Hello, your local friendly pedant here.

Not counting two 5mm f/2 refractors (my eyeballs) I have well over fifteen.

1x0.4m Dilworth reflector

2 x 0.25m reflectors (Dobsonian Newtonian and equatorial Schmidt Newtonian).

2 x 0.15m refractors (Fujinon 25x150 binoculars)

2 x 0.08m refractors (un-remembered make of 15x80 bins)

4 x 0.05m refractors (two pairs of bins)

2 x ~ 0.03m refractors (two ex-gunsights)

Sundry other hand-held refractors in the range 0.01m to 0.04m aperture, including a pair of 6x40s and some Canon lenses.

Several (between 5 and 10) 0.002 - 0.003m refractors --- aka mobile phones.

The great majority (i.e, all but excluding only a few phones) have been used to observe stars.

3 minutes ago, Mr Spock said:

With my 12" globulars are impressive. Galaxies are just grey smudges.

Tried looking at globulars in the Andromeda galaxy?

Mayall-II should not be difficult in your 12".

I'm in La Palma right now and could see Tenerife if I drove to the other (i.e east) side of the island. Although my experience of astrotourism is strictly Palmeran, there are some things which are universa in these partsl.

As noted above, cars make good power supplies. Most rental cars are fairly new and have fairly new batteries. Go for a drive before an observing session to ensure that the battery is fully charged. Take croc-clips with you to connect to the battery as you can't be sure what is available on the car.

Several outfits here in LP rent equipment. You may only need to take your camera, say, and rent the rest, or rent the mount. I am giving serious thought to providing that sort of thing myself but it won't happen just yet.

Also as noted above, check out local astronomers. Finding them will be a worthy exercise in the use of search engines and, perhaps, English <-> español translation sites.

Take plenty of storage with you, whether microSD, thumb drives, external USB drives or whatever. Make copies of your hard-won data and put one set in the hold and other in hand luggage. Data will not be covered by your insurance if it goes missing.

Paul

3 hours ago, ollypenrice said:

The first guideline is simply 'Don't.' Even quite a significant amount of dust has no discernible effect whatever.

By and large I agree with your advice, especially for Dobsonians used visually.

However, there are particular fields, in both visual and imaging use, where cleanliness is critical to reduce the amount of scattered light to a minimum and so raise contrast to the maximum. Examples include trying to detect the faintest possible objects, whether star-like or extended sources, and observing not so faint objects against a bright background, which includes things like Sirius B in the glare of Sirius, or objects in bright moonlight and twilight. Sometimes, at occultations for instance, you have no choice but to observe when the event happens regardless of the sky brightness.

What prompted me to post the above is that I need to clean the window on my Dilworth again. It was possible to perform asteroidal photometry near full moon recently but the oblique moonshine scattering off the dust on the window did hit the SNR badly.

Excellent!

I am especially looking forward to exciting new images and the latest developments in the understanding of M40.

It depends. My stargzing is entirely indoors (I'm an imager) so it can be anything I like.

In the observatory, either Cola or, more usual, hot chocolate. it's nice having a kettle near the telescope!

Beer or wine is not uncommon if I'm in the house driving the equipment over the LAN.

1 hour ago, bomberbaz said:

finally found it amongst the other stars, thanks for the link, that really helped.

I plotted a line of the asteroids course over 3 nights and then used this to compare to the maps in the link you provided.

Well done!

I've not had chance to have another go since the images I sent you.  Poor weather and social occasions.

Paul

Horizontal drizzle last night.

More of the same this lunchtime.

23 hours ago, Peter Drew said:

The one and only time that I've seen it was with my 30" Newtonian back in 1986.  It was in twilight so Sirius was dimmed but not too light to lose the Pup.  The Pup must be getting either a wider separation or getting brighter as telescopes down to a 4" seem to make it available under good conditions.  How long before someone spots it naked eye?     🙂 

I remember seeing it in a 27.5cm Mak-Cas (which I believe you made) in the very early 80's.  The orbital period (50.1 years) is such that it was about as wide then as it is now.

No-one else seems to have mentioned AP (by which I understand imaging) so here's my experience.

Full details at https://britastro.org/observations/observation.php?id=20181130_040400_1fdd8dc86f81c7d8

You may have seen https://carnegiescience.edu/new-moons-uranus-and-neptune-announced by now which reports two new satellites of Neptune and one of Uranus.

As Uranian satellites are named after characters in plays by Shakespeare, I propose that the newcomer be called "Bottom".

Does anyone here have any influence with the IAU naming committee?