A Brief Biography

Who am I? http://www.johnapurvis.synology.me
My old astronomy blog is here: http://www.johnapurvis.synology.me/sky_diary.html

Home astrobase:
Garden faces NE through South to SW.
Location: Limavady, Northern Ireland (55 N, 6.9 W).


Light pollution: this is an Orange site (Bortle class 5).

Visual limiting magnitude is about 5.5 on a good night.MW_2014_08_31


Astrophotographers have a standard way to visually assess how light polluted a site is: A 20-30 second exposure is taken with a wide angle camera lens at f2.8 at ISO 3200 (this was with a Canon 24mm f1.4L II lens for 20 secs). The above image was taken from the zenith at midnight on 31/08/2014. Its fairly yucky but there is a hint of milky way and for deep space astrophotography, I can compensate to an extent with CLS filters.

Astronomy Lists
Messier Objects (109) viewed: 90
Caldwell Objects (109) viewed: 46
Herschel 400 Objects: 104
Collinder Open Clusters (471): 54
Lunar 100 Objects: 25
Moore winter marathon (50): 36

Object Categories
Galaxies: 96
Open Clusters: 78
Open Cluster with emission nebula: 5
Milky Way Globular Clusters: 20
Andromeda Galaxy Globular Clusters: 5
Planetary Nebulae: 14
Emission Nebulae: 32
Emission/Reflection Nebulae: 2
Reflection Nebulae: 19
Diffuse Nebulae: 2
Dark Nebulae: 5
Double Stars: 26
Supernovae Remnants: 2
Supernovae: 1
Novae: 1
Asterisms: 5

Meteor Showers
Perseids: 2013, 2012
Draconids: 2013
Orionids: 2013
Quadrantids: 2014


C2014 Q2 Lovejoy
C2007 N3 Lulin


Celestron Nexstar 8SE SCT,  2000mm focal length/f10.
Finder: TS Optics 9×50, 208mm focal length/f4
Quick Alignment: Red Dot Finder.
Mount/Control: Nexstar Alt/Azimuth mount/Nexstar+ GoTo handset. Celestron GPS module.
Williams Optics 2 inch dielectric star diagonal and SCT visual back.

Kendrick DigiFire 7 anti-dew system
Tracer 22Ah LiPolymer power pack
Gerber 4 colour tactical torch – Green is good for reading.

Pentax XW series:
8-24mm SMC zoom
TeleVue Panoptic series:
TeleVue Nagler T4 series:
TeleVue Delos series:
17.3mm, 10mm
Vixen LVW series:
22mm, 13mm, 8mm
Vixen NLV series:
9mm, 5mm
Baader Hyperion series:
36mm modular aspheric
31mm modular aspheric

TS Optics variable polariser (for bright Moon).
DSO filters
TS Optics Ultra High Contrast nebula filter.
TS Optics Oxygen III nebula filter.

Solar and Lunar Astrophotography

  • Ioptron ZEQ25GT


  • Celestron C102 XLT 1000/100mm long refractor.
  • Barlow lenses: TeleVue PowerMate x 2.5, Bresser x 3.


  • CCD Camera: Celestron Skyris 274m (1600 x 1200 px).


  • Solar White light:: Baader 2 inch photographic Herschel wedge (Baader solar continuum and ND3.0 filters) plus Baader UV/IR cut filter.
  • Solar Calcium II K: Lunt 2 inch B1200 Ca K module, double stacked with 1.25 inch Baader K-line filter.
  • Solar Hydrogen alpha: Solarscope 70mm Ha filter
  • Lunar: Astronomik Red 2c filter or Astronomik ProPlanet 745 IR pass filter with William Optics 2 inch diagonal.


  • Astro-Hutech Hinodi solar auto-guider.


  • Laptop: MacBook Air (in BootCamp PC mode)
  • Acquisition: IC capture.
  • PostProcessing: Registax 6.0, Auto-Stakkert! 2, Photoshop CS3.

DSO Astrophotography:

  • Ioptron ZEQ25GT


  • Altair Astro Starwave Super ED APO triplet  480/80mm f6: 1.0 x Planostar field flattener
  • Williams Optics ZenithStar ZS71 doublet 420/71mm f5.9: 0.8 x WO6 field reducer
  • Canon 300mm f4 IS L
  • Canon 200mm f2.8 L
  • Canon 50mm f1.4
  • Canon 24mm f1.4 L


  • Canon 5D mark II
  • Canon 60Da
  • Baader modified Canon 60D
  • Canon 1100D
  • Atik Titan CCD


  • Hutech IDAS LPS D1 clip in (light pollution suppression)
  • Hutech IDAS HEUIB II clip in (HII Enhance UV and IR Block)


  • Orion 50mm  mini-guider
  • Orion StarShoot AG camera


  • Laptop: MacBook Air (in BootCamp PC mode)
  • Guiding: Stark Labs PHD
  • Acquisition: BackyardEOS
  • PostProcessing: PixInsight, Photoshop CS3


  • Canon 10 x 30 IS
    Pentax 16 x 60 PCF WP
    Pentax 20 x 60 PCF WP2

Irish Astronomical Association.


4 comments on “A Brief Biography

  1. Hi John, enjoy your blog. I see you use the Ioptron ZEQ25GT mount for AP, did you write up a posting on your experience with this mount (I may have missed it) ?

    Your results look very good, but I am very interested in this mount for my 8SE and ZWO ASI120MC (toe in the water for AP…slippery slope, to mix metaphors, I am told).


    • Thanks John!

      There’s no major astronomy shop near me so everything is bought online and after reading reviews etc. The 25 is quite lightweight but works well with my 80mm refractor which weighs in at 6kg all kitted up. I have a 4.7kg counterweight at full stretch on the other end (have just bought the extension arm). The ioptron iPad app helps greatly with getting an accurate polar alignment.

      The Orion 50mm mini guider/PHD combo seems to work really well with my current setup. I’ve been gradually pushing up my sub lengths to 12 mins and so far the mount/guider are coping really well.

      I also have a 8SE and would like to use it for the tiny faint fuzzies but I read that you have to use off-axis guiding with SCTs because of primary mirror movement so I’m putting off learning that skill for another day.

      I think the whole issue of which mount boils down to weight. I think the quoted weight for the Nexstar 8SE tube is just under 6kg, put that up to 8kg to allow safely for mounting rings, guiders etc. The rule of thumb for astrophotography is to keep scope weight to no more than 50% of quoted payload of 12.3kg for the ZEQ25GT so I think you would be over that limit unfortunately. Unless you can find someone on the Internet with that combo who endorses it.

      I’d love to get a Williams Optics 102mm GTF at some stage but will probably have to upgrade my mount to something like the Ioptron 45 – haven’t checked the maths on that one yet.

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