Some activity in white light

I have finally seen some activity on the Sun on white light. The image shows faculae (just, if you squint !). This faculae are visible in a number of images taken over several minutes, so are not figments of my imagination.These are brighter than  normal areas and can be associated with sunspots (cooler than normal areas). According to Spaceweatherlive a sunspot group is due to appear from the side of the Sun away from the Earth any day now, so maybe this is preceding it.

  

DSLR Photometry

Last night I had another go at gathering some data for X Herculis, using the Canon 500D DSLR on the Skywatcher 80ED Pro. This time it was much more successful. Suitable settings to collect useable data from stars in the range  6 - 9 Visual magnitude are:

                                     400 iso
                                     30 second exposure
                                     Telescope focussed , then defocussed by 75 % of a turn of the fine focusser

X Herculis in centre of field

Together with  suitable flats, bias and dark frames, I processed the images in IRIS (from AAVSO):

IRIS data being processed

The screenshot above shows the calibrated and registered image of X Herculis having its instrumental magnitude being measured. The annulus around the star is used to measure the 'darkness', compared with the inner ring, the star. The same is done for a number of comparison stars and the difference between 'instrumental' magnitudes is added to the magnitude of a star of known magnitude to find the estimated photometric magnitude.

Problems this time:

The field of view for this target is too wide for my telescope, so I need to find a variable star with comparison stars within a 2 degree FOV.

Quiet Sun

It's about the eighth day without any sunspots or faculae. I made my filter 6 days ago...

A Quiet sun, showing limb darkening and not much else

The Baader filter blocks out 99.9999% of light. Even so, to take the phot I have to use iso100 and a shutter speed of 1/1600s.

Variable Star Photometry

Back in the 90's I recorded the apparent magnitude of a number of stars known to change their brightness, sending off the information to the British Astronomical Association (BAA). To record the magnitude, I used a pair of binoculars to find the star via a chart provided by the Variable Star Section of the BAA. I then compared the brightness of the target star with stars of known brightness that did not change. All this ended when I broke my binoculars and , at that time, I was not able to afford a new pair.

Zoom to present day.

Two things, one being I have thought I would resume taking some variable star measurements, plus, we are going on holiday to Aquitaine where there should be really dark skies. I toyed with the idea of buying a pair of Celestron 20 x 80 binoculars, but in the end decided the steadier platform of a small Dobsonian would be more pleasurable to use. So, I bought a second hand Sky-Watcher Heritage 130P FlexTube Dobsonian Telescope. It looks like a toy, but has a 1300 mm parabolic mirror that is really good quality. Marrying this to y Televue 25 mm Plossl or BST 25 mm Starguider  and optically, I have a very nice telescope indeed. It is very portable, easy to use for star hopping, has a field of view of just under 3 degrees (with the BST 25 mm Starguider eyepiece) and the only electronics are the red dot finder.

I did a few mods, one ot add some thick grease to the helical focusser, to remove the slop, to add a couple of velcro patches to make the telescope tube cover  more likely to stay on and to  add a little extension piece and a bigger red dot finder to make it more usable, especially for targets close to the zenith.

I have used it to take a few readings of X Herculis and AC Herculis.

I have also tried doing some DSLR Photometry, with the Skywatcher 80 ED Pro. That involves finding the traget variable star (via  Carte Du Ciel), defocussing, then taking images  but making sure the stars are not saturated. I have had one attempt so far, but I think I defocussed too much ( 1 1/2 turns of the fine focus). When I tried using IRIS (from AAVSO), it had problems identifying stars at the registration stage.

So, next time, I shall be trying iso 400, 30 s exposures and  3/4 turn fine focus to defocus.

Solar Astronomy

So, the telescope is sitting htere, it is the time of year when there is no astroniical night, what can I do?

Look at the Sun! So, after buying a pack of Baader Solar film and following the instructions to make a solar filter that fits over the dew cap of the Skywatcher ED 80 Pro, I am no able to take images and video if the Sun in white light. The colour cast in the photo is because I am not bothering to remove the  Light Pollution filter from the camera. So far, because the Sun is at solar minimum, there have't been any faculae or sunspots.

What can be seen (just) is the limb darkening and a hint of the granulation.
Limb darkening is an optical effect seen in stars (including the Sun), where the center part of the disk appears brighter than the edge or limb of the image.

Granules on the photosphere of the Sun are caused by convection currents (thermal columns, Bénard cells) of plasma within the Sun's convective zone. The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation.

Telescopes come and go

Scope changes......

Even though I really liked the Celestron XLT 6, with my current mount, it wouldn't have been practical to have set up a guider on it, so I decided to reinstate the Skywatcher 80ED Pro and said bye bye to the Celestron.

After a couple of sessions where the tracking was AWFUL, I was contemplating paying the £300 to have the Celestron CG5 GT mount hypertuned.  However, after re calibrating the mount for PHD2 and now using 2 alignment and 2 calibration stars, plus polar alignment (Celestron software via Nexstar +), the tracking has been really good.

Owl Planetary Nebula in Ursa Major

North America Nebula in Cygnus

Ring Nebula in Lyra

Iris Nebula in Cepheus

It's been a while....

1. Not really mentioned it before but since the end of January 2019 I have had an observatory shed ! It is now on Shed 1.1, the main changes being making some of the cabling positions more permanent. The opening roof isn't causing any problems and has been completely water tight . The main issue overall was the adhesive I used for sticking foam seals along the edge of the opening roof hardened and then disintegrated. So, this was replaced with silicone, which hopefully will be more durable and remain flexible.