Last updated: 11 April 2004

Subject: Venus Transit & Sunspot Series Ideas
Date: 4/8/04, 23:30
From: Dan Prall (
ETX users and others:

Here are some ideas for the upcoming Transit of Venus across the face of
the sun on 8 June 2004; first time since 1882.  If you miss it, your
next chance is in 2012, and after that 2100+ [crank up those eternal
nanobots or alert your great-great grandchildren].  It will be visible
at least in part from the eastern US, all of Europe and Africa, most of
Asia, and parts of South America and Australia.  Webcams will be good
for high-magnification shots of both ends to capture the entrance/exit
of Venus on the face of the sun, but for the rest of this hours-long
event, a digital camera might be a better choice.  There are also some
ideas on following sunspots at any time.

The attached example shows some ideas on capturing with a digital camera
that can be mounted to any telescope, but my personal objective is to
shoot with a Meade ETX90RA I bought recently for that purpose, and
generally as a travel scope I can fit into carry-on baggage.  I'll be
using it with an Olympus 3.3 Megapixel camera, C-3000.  Much of this
will be gear-specific, but should be adaptable or spur ideas for other
setups.  I've included a LOT of detail on the idea that too much is
better than not enough.  Use what you need and ignore the rest.  This is
rude and crude and I could take another week to polish it, but time and
tide and the Venus Transit wait for no man. [I didn't write it: OK, "for
no person".]

I'd iron everything out before posting this, but the date of the transit
won't wait.  I'll be watching the transit from southern Turkey while
checking options for the March 2006 total solar eclipse.  For daily
series of sunspots, see toward the end, but many of the tips for the
transit also apply.

See figure for how to judge and compare your shots.  Remember, these
were taken with a 90mm aperture.  I picked ...2154 as the best of the
series in the example.

A few months ago I bought a "vintage '1997'" new ETX90-RA powered by 3 AA batteries with tabletop tripod for about $170 to be my travelscope. It was small enough to fit into a carry-on bag, along with accessories, cameras, battery chargers and minimal old-guy pills [I'm 63], a toothbrush, and one change of socks; everything else could go into checked baggage. Carrying it on means less potential damage than checking it and crossing my fingers from Dallas to Antalya. I bought a Philips ToUcam 840 and got 1.25" adapters for it from Steven Mogg in Australia; about 9-10 days shipping to Dallas. However it now seems that it'll be a peripheral system and my Olympus digital camera will be primary. I bought an adapter to fit my Olympus C-3000 3.3 Megapixel digital camera with a mount to fit Meade Plossl eyepieces from Shutan in Chicago, but other stores have similar gear. For whole-sun shots, the 40mm Plossl is best, tho the mount will also fit other similar Meade eyepieces for magnified sunspots. Adapters are available for most pro-sumer recent digital cameras with screw-threads on the front of the lens. In the area where the entire transit is visible, it lasts about 7 hours. Using the LCD screen gobbles batteries, so be prepared with another power source or several backup battery sets. I've found that customizing settings for spot-metering, macro, and ISO 100 work best with the P[rogrammed] setting. Carry a small magnifier for focusing, or fine-focus the ETX before the event and paint-mark the focus settings, even better. If you're using a webcam too, prefocus and mark those as well, noting the number of turns of the focus knob. BE PREPARED! Practice everything well in advance. With the C-3000, if you have fairly clear skies, I suggest shooting at the highest TIFF setting. With my camera, this means about 30 seconds' recording between shots, and a 128Mb card will hold 13 shots, versus 70+ at the highest SHQ setting. Be sure to customize it so that shots are numbered continuously, rather than resetting with every new card to eliminate having to download to different folders, to save time. My count is at about 2200, so I'm safe until it rolls over at 9999. Lets say the transit lasted 8 hours and you want to take 10 shots every 15 minutes as TIFFs. That means you'd do best with a team of two MINIMUM working to download the shots via a separate reader to a computer, while swapping at least two 128Mb cards. One TIFF is 9.231Mb, so round up to roughly 10Mb. That means 10 shots every 15 minutes over 8 hours means 3.2Gb of disk space to save the originals. On my AMD laptop running at 1.667GHz it takes about 4 minutes to transfer those shots to the hard drive. On June 8th, for the complete transit, using that formula, to get 32 shots, you'd need: A team of 3 or 4 is best; it's on a Tuesday, so you need the retired or unemployed. Probably 4 128Mb storage cards [based on 10 shots per card, and recycled]. A computer to download images. Lots of sunscreen or a great tan. Lots of water to drink. Lunch! Practice drills in advance. [by e-mail?] A written plan with a copy for each team member. Provisions for bathroom breaks for all team members, so everyone or at least two should be able to shoot or operate the computer enough to download the shots, if needed. In reality, time is a bit less. Estimate 30 shots at 15 minute intervals. If you're doing it solo, estimate maybe half that number at 30 minute intervals, or whatever fits your degree of fanaticism, but for ~10Mb TIFFs, figure 10 shots. By the way, it will take about 7 minutes to shoot and record them in camera as TIFFS! Why shoot 10 when one will do? Remember that residual vibrations from touching and wind shake all count at these magnifications. Of course, if you are using a larger aperture scope, camera remote, sturdier mount, etc., you'll get better results, all things considered. I seem to get one or two decent ones out of ten. See the example for my squinted eyeball pragmatic pick-'em technique. Whether you shoot TIFF or Hi-Q jpg, the stability or lack of happens at the instant of exposure. In the event that you have only a few moments between clouds, the SHQ jpg setting is a good compromise between speed and resolution. Normal photos at that settting are about 1.5 to 1.7 Mb. Solar shots are about 1/3 to 1/5th that size, so I can get a few hundred on one 128Mb memory card. They shoot and store much faster. Shoot lots and pick the best shot later under those conditions. But for clear conditions, shooting TIFF and later conversion to BEST-Q jpg in PhotoShop gives the best results. 30 images should be enough to make a good animation, which you can do with PhotoShop or PhotoShop Elements. As to my webcam, I may use it first and last. It requires a laptop hookup for capture as an AVI, and its 640x480 resolution means almost one Mb per frame captured and another 900Mb per frame if you convert an AVI to BMP's. The entire 7 hours would mean about 125Gb of disk space to record, not to mention more to process and store the individual frames, and it might be a lot more. Anyone have a portable affordable self-powered terabyte hard drive? Not this year. Maybe in 2008? The webcam doesn't allow full-disk sun options, so I'll use my Olympus as my primary for the transit, where full-disk views are important. This should show up on Weasner's site early enough to buy the gear, test it on sunspots, and book your trip to a sunny spot in southern Europe before 8 June 2004. If you're more interested in sunspots, much of this applies. Think about full sun shots and capturing over several days to make an animation. If you have friends in other locations where you're not likely to be clouded out at the same time, you can agree to shoot at about the same GMT time every possible day when an interesting sunspot group appears, and maybe one of you will get a shot the other misses for clouds. An hour or two either way makes little difference; the sun rotates once in about 28 days, so a spot should cycle from one edge to the other in 14 days. As I write this, I'm working with a mate in Australia to shoot the current group. I plan to shoot in the late afternoon in Dallas. He shoots in the morning and it matches closely. Depending on who's on daylight time, our difference is 7 to 9 hours. Miniscule differences for a few hours. We both use GMT for a common time base. UT for all practical purposes. Find a few contacts in remote places who want to shoot sunspots with commercial consumer+ digital cameras. Agree on GMT times in common to shoot. The primary remaining factor is the orientation of the camera. Since the solar subject is a featureless disc except for for the sunspots, it's best to agree first that the camera will be oriented in a way that a simple 'flip' will align shots from two or more observers, without having to rotate by some arbitrary angle. Exchange shots over 14 days or more. Process thru Photoshop or other. Here are some useful links as of late March 2004: Transit observer See positions of Venus and the sun at preset cities or enter your location. For the transit, click "Watch 2004 Transit" and click the map to set location; then you can step by hour or minute. Map: Cities: Animation as seen from Belgium Here's a suggested numbering system to coordinate sunspot shots from several places: use GMT to label the time they were taken, and two initials to show who took them. Spots_04_03_26_23_18_16_GMT_DP.jpg yr mo dy hr mn sc zone who [i.e., DP for Dan Prall] For example, this shot was taken at: 2004 March 26 23:18:16 GMT by DP. Most info on when it was taken is available to camera programs, assuming the camera time is accurately set. This one was taken at 5:18:16 PM CST at my home in Carrollton, Texas on 26 March 2004; with a six hour difference between Dallas and GMT, 5PM is 17 hours, or 23 hours GMT. Don't neglect to factor in daylight time changes. This system will work for sunspot series until late 2099. Let your great-grandchildren work on a better numbering system, not that they will, because kids have no respect these days* and aren't likely to have any more in the future. Hey; if you decide to stick them with the bill for your tax break today, it's only fair when they decide to cut off your life support tomorrow. It also allows self-ordering by name in Windows Explorer. A world-wide group of coordinated users taking photos every few hours and sharing files would make for better ordering using this system; use as many or as few shots as you like; they'll order themselves by name. With many files, yours may or may not be used in one series, but don't let that stop you from contributing and sharing. Maybe you thought you had nothing to contribute to astronomy because your telescope was too small or you didn't have enough time to spend hours with it in a session? Not so! The idea to coordinate shots from different places and the file numbering system came from Wally Anglesea of the Illawarra Astronomical Society who lives in Dapto NSW, south of Sydney, AU. See his work and coordinate with him at: There are many details left to be ironed out for sharing standards. For example, my Olympus C-3000 saves at 2048x1536, and Wally's Kodak DC 4330 saves at 2160x1400, but those differences can be resolved in programs such as Photoshop or Photoshop Elements. All these details can be worked out in a community of shared images. I should have it all together by time for the transit. I hope..... Dan Prall

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