Entries tagged as teleconverter

Saturn and its satellites

Rhea - Tethys - Saturn - Dione - Titan on June 15, 2016

I used the Opteka 2x teleconverter lens for astrophotography for the first time when I took another series of photos of the planets two days ago. This is supposed to be used with telephoto mirror lenses, but that's basically what my telescope is as well and I hoped it would be usable here. Test shots during the day came out alright, maintaining better contrast than the 2.5x Barlow lens I had been using. As you can see here, it performs reasonably well in the night, too.

I didn't originally intend to photograph the Saturnian satellites because they are quite dimmer than the Jovian ones. The four biggest Jovian satellites have apparent brightness in the magnitude 5 range, while the biggest and brightest Saturnian satellite, Titan, is around magnitude 8. The three largest after Titan are of magnitude 10. That's why I didn't take separate photos with longer exposure. Even so, post-processing the background area revealed the dim satellites. I noted their relative positions with the caption. Dione may be barely visible on on well-tuned screens.

Telescope: Celestron NexStar 6SE + Opteka 2x Teleconverter
Device: Sony A5000 (prime focus)
Settings: (3000mm) - ISO 100 - 1/3s - (f/10)
Filters: None
Time: 2016-06-15 00:12-00:13 KST
Location: Naju, Korea
26 photos stacked with PIPP 2.5.6 and RegiStax

Is a teleconverter worth investing?

Two indoor, two outdoor shots using pure Canon SX50 HS at 50x zoom (center), Raynox DCR-1540Pro (left) and Vivitar 2.0X (right) teleconverters
Raynox DCR-1540PRO vs. Canon SX50 Original vs. Vivitar 2.0X

That's the question I had in the attempts to extend an already powerful 50x optical zoom on my Canon SX50 HS. The results aren't very impressive.

I bought two teleconverters for testing. The cheap one is a Vivitar Titanium 2.0X, at about US$40. The expensive one is a Raynox DCR-1540PRO with 1.54x zoom, at about $200. Unfortunately, the latter had been discontinued a long time ago (it came out at least in 2003), so I had to buy a dusty used one at half the price.

The collection of crops above really tells it all. The cheap Vivitar is trash. Completely unusable, chromatic aberrations and all. It works okay at low zoom, but that defeats the purpose.

Meanwhile, the expensive Raynox has been advertised as "for 25x or higher zoom" and "340lp/mm at center", so I was expecting better. Well, the colours are fine but it doesn't come into focus as well as I would want it to. Even at the best spot (seems to be at lower center region, not outright center for SX50 HS) it doesn't really add more detail. This might be usable for video mode, but not much value for still photos.

As for the actual multiplication, close (~5m) shots got about 1.3x for Raynox and 1.4x for Vivitar, getting roughly about half the spec. Far (~250m) shots are better, at about 1.52x for Raynox and 1.8x for Vivitar.

If anyone's searching around to see if one needs a teleconverter for a SX50 HS, I can easily tell you "don't bother".

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