Paul McKay

DIY Polar Scope Illuminator for EQ5 Mount

I recently bought a 2nd hand Sky-Watcher Explorer 200P on an EQ-5 mount off AstroBuySell and was pleased to discover that it came with a polar scope. For the unitiated, these are used for aligning the polar axis (that’s the extra one that alt-az mounts don’t have) to the north celestial pole so that objects can be tracked by moving the scope in the Right Ascension (RA) plane only. Alignment requires sighting Polaris through the polar scope so that it aligns with a specially engraved reticule inside the polar scope eyepiece. The problem is that when its dark, the reticule markings cannot be seen so have to artificially illuminated (but not too much otherwise it swamps the stars!)…by a polar scope illuminator. Of course, you can buy one at £23 but reviews of them were very mixed so I researched how to make one, after all it’s only a fancy dim torch how difficult can it be?

The description below is really a prototype (with help from utube) as I tried various options while making it. The bought ones fit on the eyepiece but mine fits on the inside the hole in the mount at the ‘objective’ end.

Parts Needed – plastic

From Screwfix, Wickes or Discount Store, Swadlincote

  • 32mm plastic equal tee with compression joints –– about £3.
  • 32mm socket plug – £1.20
  • 40mm socket plug – £1.20
  • 32mm PVC pipe – £2.40 for 3m – we need about 250mm! Try to find an off-cut.

Parts Needed – electrical

From RS Potts Babbington Lane, Derby

  • Small red LED
  • Small rocker switch
  • AA double battery holder
  • 1W rated resistor
  • Small connectors (3)
  • Low voltage cable
  • Insulating tape, or earth wire insulation
  • M4 screw, nut and washer
  • 2 x AA batteries

I had some of these already but I bought the LED, resistor and battery holder for a total of 94p.

Method – refer to photos

Cut the pipe into 2 pieces: 100mm for battery/switch compartment and 50mm for inserting into mount. The longer piece and the branch stub of the tee need to be cut to fit the rocker switch, making sure it faces downwards for easy access when looking through the polar scope. Cut away the flange of the 40mm plug to form a neat end for the battery compartment.

For my mount, I needed to reduce the diameter with a rasp/coarse emery for it to fit snugly inside the hole in the mount. This was a pain by hand but would take only minutes in a lathe.

I made a support (12mm x 150mm but length depends on your mount) for the wires to the LED from a 150mm length of pipe and bolted it to the bottom stub of the tee with M4 screw/nut. Tape wires to the support to keep them out of the field of view.

The 32mm plug is just a cap for the top plug when not in use. My photo shows the branch of the tee curving upwards but it’s better to arrange it curving downwards (remember mine is a prototype!).

Wire up the battery compartment, switch, resistor and LED (polarity is important for the LED). Carefully measure the lengths of wire needed to avoid excess. Soldering is better but I used small plastic connectors. Use tape or insulation to cover any bare wire connections.  Fit the batteries and test. If all ok, carefully thread the wired assembly into the tee piece and your ready to try it out. The support and position of the LED may need to adjusted/bent to avoid it shining directly into the polar scope.

You have a polar scope illuminator for about £10. At the next opportunity, I will attempt to take a photo of the view through the polar scope when illuminated and add to this post. Feel free to ask questions. To finish I would like to hear details from anyone who uses a 90 degree viewfinder on their polar scope, its a long way down to the eyepiece without one.

Illuminator Fitted to EQ5 Mount
Finished Assembly
Exploded View

Wake up to Venus and the Moon

My first shot of Venus at 7.40am on Friday 30th November through my Skywatcher 200p with a Canon EOS60D. I assume the blurry image is due to it being quite low and that the planet is always cloud covered.

Just to check it was not any fault of the optics I took a few shots of the Moon high in the sky at 3rd quarter, always a fascinating photographic subject. I particularly like the way the Sun is catching the peaks of the Apennine range.

Morning astronomy sessions seem to suite me more than late evening ones but there is always the race against time before the Sun rises. I need to set everything up the night before!

Many thanks to Lee for checking and collimating my scope and explaining a few of the basics to me on a busy evening last Friday.

Moon through SW 200P

Hi All Having just acquired my first telescope I was keen to try it on the easiest of objects, the Moon. To a relative novice, the detail visible was truly awesome. I am not set up with T ring and adaptors yet to connect the Canon DSLR but could not resist putting my compact Panasonic TZ4 to the eyepiece, hence to low photo image quality. My only criticism of the EQ5 mount is finding and reaching the RA control knob around the bulk of the 200mm tube. Control cables are now on the Christmas list.

Big thank you to our chairman, Andy for his advice and guidance on checking out a secondhand telescope.

Skywatcher Explorer 130P with AZ EQ Mount

Hi All , I have been reviewing what telescope to buy for a while and at the forthcoming IAS I hope to see some in the flesh and decide. While on the internet, I found on a mount that can be converted from Alt Az to EQ used on the Skywatcher Explorer 130P – see link and photo (although I would prefer the 150P).

Does anyone have experience of this type of mount. I have no experience of actually using an astronomical telescope, but can any EQ mount be used in Alt Az mode just be aligning the polar axis vertically? I would be interested in the views of anyone with experience of a mount designed to be converted  from one type to another? Are they a compromise that end up not performing well in either mode? Thanks in advance.

GCSE Astronomy – Result!

Hi All

I’m still a new kid on the RAG block but some of you will know that I completed an online Astronomy GCSE this year. Well, I have just received my result:

a Grade A (83.5%) overall, 78%  in written exam and 100% for my coursework. I am feeling very pleased, especially as I thought the exam was really tough. If anyone wants advice on doing this over the coming year then please ask. Its a great way to grasp the basics of man’s oldest science that pre-dates the written word!

Open University Astronomy Course

Hi All Having taken a GCSE in Astronomy this year, I am now thinking of progressing to an Open University course called Astronomy and Planetary Science. It is a level below degree but looks ideal for me. Before I take the plunge (its quite expensive) I wondered whether anyone has any experience of this or other OU astronomy courses?

Also, does anyone or the Group have copies of the 2 textbooks?

An Introduction to Sun and Stars 2nd edition (2015) by Green and Jones,

An Introduction to Galaxies and Cosmology 2nd edition by Jones and Lambourne.


Jocelyn Burnell Lecture at Jodrell Bank Discovery Centre

Since retiring a year ago I have rekindled my casual interest in astronomy by taking an online Astronomy GCSE course, joining the RAG and visiting places of astronomical interest, such as the world famous radio telescope at Jodrell Bank, Cheshire. During my visit there on 1 February 2018, a famous astronomer, Dame Jocelyn Burnell was delivering a lecture on her discovery of pulsars in 1967.  She’s famous not only for this discovery but also for her controversial exclusion from the Nobel Prize in Physics for the discovery.

Jodrell Bank Radio Telescope

Although the radio telescope is an impressive feat of technology and engineering, the highlight of my visit was the lecture. The event sold out shortly after Christmas and so all 200 seats in the auditorium were occupied, she was obviously very popular with the astronomer fraternity.

She explained that the objective of her PhD was to discover more quasars (quasi stellar radio sources) but first she had to build her own radio telescope, and for this, like all fellow astronomy students back then, she was given a tool-kit; rugged pliers, wire snips and a screwdriver! Cambridge still used valves in their amplifiers, although transistors were available at the time! The new telescope covered several acres, used miles of cable, took 2 years of working in all weathers to complete and worked first time! It was a fixed structure, with no control over its direction.

Launch of IYA 2009, Paris - Grygar, Bell Burnell cropped.jpg                                                                                   Dame Jocelyn Burnell                                                                                 

She confessed to being so surprised at getting into Cambridge University that she was sure the University had made a grave mistake and she would be thrown out as soon as this was discovered. In the meantime, she would work flat out to get as much done before this happened. This, she said, was the incentive that drove her to work long hours and to accept the brunt of supervisor’s caustic comments.

The main task was inspecting miles of printout for anomalies and it was not long before she found one…then another…and another. It was a sign of the times that her supervisor (and recipient of the Nobel Prize) was arrogantly dismissive of her excitement and was told the source was not from outer space because of the pulse’s incredible regularity, it must be man-made interference.  And so began a laborious period of eliminating all possible spurious radio sources; badly suppressed vehicles, radio waves reflected from a corrugated iron shed roof and even from the Anglian Police Force radios. With an ironic smile she recalls telling her supervisor that if a vehicle was to blame it was setting off at 4am, then at precisely 4 minutes earlier each day and had been doing so for the past 2 weeks! The source was clearly emanating from the same point on the celestial sphere. With wry humour, she told how she played along with notion that it could be a man-made source, labellng the first anomaly or ‘bit of scruff’ as LGM-1; Little Green Man-1.

She recounted that to check the recurrence of one source she would need to be using the telescope at 2am but she was due to go to her home in Ireland with her fiance that day to announce their engagement…she duly stayed up all night and also made it home. Such was her determination.

With standard plotting paper speed the anomalies were too compacted to be analysed accurately, so the paper speed had to be  increased. But this meant each paper roll would last only 20 minutes. The solution was to only increase the paper speed just before the predicted time for the repeat showing of the anomaly. Unfortunately, this meant going out to the telescope control shed in the middle of the night sometimes.

We now know (partly due to astronomer Sir Fred Hoyle) that the anomalies are pulses from neutron stars rotating very rapidly and with incredible regularity, the LGM-1 has a rotation period of 1.3 seconds. Strong radio signals are emitted along the axis of the magnetic field and because this is inclined to the axis of rotation, the radio beam points in the direction of Earth once each rotation, causing it to pulse like a beam of light from a lighthouse.

Artist conception of a pulsar with its magnetic field lines and particle jets

Pulsar: a rapidly rotating neutron star with a strong magnetic field

During an interview with a reporter from the The Guardian she was asked what the new stars were called. Burnell said she had been too busy to think about it. The reporter suggested an abbreviation of pulsatiing radio star, and that was agreed.

During the post lecture questions Burnell was asked by one of the school children in the audience about being overlooked for the Nobel Prize. She has obviously fielded this question may times and her stance is well known; research supervisors take the flak if the project flops and the credit if it succeeds, no matter how well, she explained. In those days, students were regarded as ‘support’, the ‘labourers’ poring for hours over paper charts, whereas the supervisors initiate and direct the research and as such deserve the credit. She is clearly not bitter, and has received many other accolades and honours as ample compensation. She claims that by not getting the Nobel Prize, she is in good company. She is right, take a look at the achievements of Cecilia Payne-Gaposchkin (composition of the stars) and Henrietta Leavitt (Cepheid period/luminosity), both worthy candidates.